I do hope she is not pregnant, but as others have said, she NEEDS a vet visit to determine this and for her own safety. If it turns out she is not pregnant, you should have your mom look into a low cost spay program in your area (partners with the ASPCA). Here is the search link; I hope if she's not pregnant this will be your (and your mom's) next step. Good luck.
ASPCA | Low-Cost Spay/Neuter Programs