1.  The landlord shall at all times during the tenancy maintain the dwelling unit in a habitable condition. A dwelling unit is not habitable if it violates provisions of housing or health codes concerning the health, safety, sanitation or fitness for habitation of the dwelling unit or if it substantially lacks:

      (a) Effective waterproofing and weather protection of the roof and exterior walls, including windows and doors.

      (b) Plumbing facilities which conformed to applicable law when installed and which are maintained in good working order.

      (c) A water supply approved under applicable law, which is:

             (1) Under the control of the tenant or landlord and is capable of producing hot and cold running water;

             (2) Furnished to appropriate fixtures; and

             (3) Connected to a sewage disposal system approved under applicable law and maintained in good working order to the extent that the system can be controlled by the landlord.

      (d) Adequate heating facilities which conformed to applicable law when installed and are maintained in good working order.

      (e) Electrical lighting, outlets, wiring and electrical equipment which conformed to applicable law when installed and are maintained in good working order.

      (f) An adequate number of appropriate receptacles for garbage and rubbish in clean condition and good repair at the commencement of the tenancy. The landlord shall arrange for the removal of garbage and rubbish from the premises unless the parties by written agreement provide otherwise.

      (g) Building, grounds, appurtenances and all other areas under the landlord’s control at the time of the commencement of the tenancy in every part clean, sanitary and reasonably free from all accumulations of debris, filth, rubbish, garbage, rodents, insects and vermin.

      (h) Floors, walls, ceilings, stairways and railings maintained in good repair.

      (i) Ventilating, air-conditioning and other facilities and appliances, including elevators, maintained in good repair if supplied or required to be supplied by the landlord.

      2.  The landlord and tenant may agree that the tenant is to perform specified repairs, maintenance tasks and minor remodeling only if:

      (a) The agreement of the parties is entered into in good faith; and

      (b) The agreement does not diminish the obligations of the landlord to other tenants in the premises.

      3.  An agreement pursuant to subsection 2 is not entered into in good faith if the landlord has a duty under subsection 1 to perform the specified repairs, maintenance tasks or minor remodeling and the tenant enters into the agreement because the landlord or his agent has refused to perform them.

      (Added to NRS by 1977, 1336; A 1999, 1229; 2007, 1284)

What kinds of things is she requiesting?  Beyond these any any applicable state or local building code requirements, there is little else you must do.  Of course, you must make necessary repairs.  But other items don't need to be done.  Tell the tenant it is your policy that all repair requests be placed in writing and sent to you unless it is an emergency (fire, flood, electric sparks, or structural problems).  All others have to be put in writing.  If she calls for something, let the machine pick up.  If she wants work done, call in a day or so just to remind her it has to be in writing (for record keeping purposes).

Once you get the request, it fals into one of 3 categories.  1) Emergency or urgent - you begin repairs within 48 hours.  2) Needed or necessary repairs - you schedule work within 30 days.  Or 3)  Unneeded or cosmetic repairs - You deny this request.  Once you figure out which it is, you send a notice to the tenant saying something like "Per your request dated xx/xx/xx, the work you have requested is (then mark 1, 2, or 3 above).  Then you state when the work will be done or say "Sorry, but I must deny this request as this work is not necessary to the habitability or use of your unit."  Not all work requests must be honored.  If the request is for an upgrade, a cosmetic issue, or an aesthetic issue, you simply don't do this work while the unit is occupied.  You wait until it is empty.

Some examples of each type of request:

1)  emergency - stopped up toilet (only one bathroom), tub, or kitchen sink, fire, broken pipe, flood of unit, emergency structural (tree fell on house, storm blew off roof), sparks from outlets or electrical appliance, non-funcional stove (not the loss of one burner -  but the oven, or all the burners) or fridge, loss of heat in winter, large roof leaks, break in to unit, door lock is non-functional, no hot water, broken window (open to elements)etc.

2)  needed - repair of stopped up toilet (when more than one bath), bath sink, one non-functioning burner on stove, very small roof leak, one non-functional outlet (no sparks, just doesn't work), sticky or loose door lock, thermostat or furnace needs adjusted (but still produces heat), less than desirable amount of hot water, washer or dryer (yours) non-functional, small leak in unfinished basement, A/C repair in heat of summer, etc.

3) Unneeded - new paint, new carpet, repair to hole in wall (not present before occupancy),  new handles (providing they still work), install A/C (if they rented unit without it) repair screen (some areas can require these, but if they were already present, you don't have to repair them until they vacate), install more than required number of smoke detectors, install doorbell, new deck, stain deck, side house, replace unbroken windows (more energy effficient ones wanted), etc.

I could find nothing that says appliances must be provided in the state law.  The passage above says you must maintain those you provide or those that are required to be provided, but it doesn't say you are required to provide them.  You will have to miantain them now that you have provided them.  There may be a local ordinance that says appliances are required, but you would have to check that. 

You can easily require a tenant to replace their own filters.  This is simple and routine maintenance and is no harder than replacing the batteries in the smoke detectors.  If she wants to hire a service to do it (and she did) she pays for it.  I wouldn't pay that bill, I would give it to the tenant to pay.  You were not informed of any problem, she did not request service from you first, so she has no legal right to call in a contractor to do this.  Don't let her get by with this.  Once you pay for this once, she will be calling people to do all sorts of things and you will start receiving bills. Send her a copy of the bill to pay or to reimburse you for it.

I don't change filters for the tenant.  I show them where they go at move in and they are responsible for this from then on.  I put it in the lease that they must be replaced monthly and any service call that results from their failure to replace them is their responsibility.  Next thing you know she'll be wanting you to change her burned out light bulbs!  (Don't laugh, I have seen tenants try and demand this!)  You need to let this tenant know you are in charge.

Immediately send her notice with this bill that she is to notify you in writing of any service or repair that needs to be done in the unit.  Let her know that you will not pay for any service that she initiates and that she will be billed.  Write on the bill that it is due with her next rent payment.  If she fails to pay it, deduct it from her next rent, mark the receipt as the service bill paid, but rent is lacking and send a pay or quit for the balance of the rent.  You must take charge of this tenant.  She will only grow more bold each month if you don't.