http://www.bio.miami.edu/hare/opcare.html
^ from Dana Krempels, Ph.D.
“Pain Management
Any surgery, including a neuter or (especially) a spay, will make bunny sore for one to several days.
• Pain management in rabbits is critical to uneventful recovery.
• Most experienced vets routinely administer analgesics such as metacam/meloxicam, Banamine (flunixin meglumine), buprenorphine, tramadol, etc. before or shortly after surgery, so the bunny will be as comfortable as possible while waking up.
• Ask the veterinarian about this before scheduling surgery. If no pain medications are going to be given to your rabbit, you should probably seek a different vet!
• Before bringing your bunny home, ask your vet about follow-up pain management at home, when the initial dose wears off. ”
General Pet MD site: https://www.petcoach.co/article/spaying-and-neutering/
“Rabbits in pain become stressed and will not eat, which can result in serious complications. The use of analgesics (pain relievers) in rabbits is important to reduce the recovery time.”
From House Rabbit Society, includes clause about pain management after procedures: https://rabbit.org/the-importance-of-analgesia-pain-control-for-pet-rabbits/
“Drugs (oral, injectable or transdermal)
Opioids – these drugs are related to morphine and there are several safe and effective candidates in this category. They are most often used for bone pain and as part of a pre and post surgical pain management protocol. These drugs are most often given by injection, but some can be given orally or as a transdermal patch on the skin.”
— I have a male, so no experience with post-spay recovery, but considering that even a male neutering, which is a much more simple and less invasive procedure, requires pain meds afterwards, pain meds after a spay only seems logical. You can explain to your mother what a spay is, maybe that will help. I warn you the images on this site are graphic, as they show the operation, so if you do not want to look, do not, but maybe show them to your mother so she can see how this is no small operation: http://www.medirabbit.com/EN/Uro_gen_diseases/castration/Spay/Steril_en.html . The end does mention post-op care, which includes the heavy recommendation for pain medications
The answers provided in this discussion are for general guideline purposes only. The information is not intended to diagnose or treat your pet. Seek the advice of your veterinarian or a qualified behaviorist.