See if your mom will have a consultation visit with your vet. She can ask all the questions she needs & I'm sure the vet will set your moms mind at ease.
Your vet may even do this over the phone.
Call your vet & see if you can talk to him, ask him if he can talk to your mom (as long as your mom agrees to it). Make sure your vet gives your mom all the pro's & con's of having it done.

Here's a couple articles you can show your mom:
http://www.hsus.org/pets/pet_care/wh..._your_pet.html http://www.almosthomerescue.org/spay...spayneuter.htm