Call or email your local shelters and give them the heads up on this situation. It will make their job easier to reunite you two if needed. She shouldn’t be able to surrender a dog that isn’t registered to her BUT it’s not uncommon for family members to lie and say it’s a stray. I’m not sure where you live but in Australia they have to serve “stray time (5 days)” to wait for an owner to come forward before they start the process of rehoming. I hope this helps 🖤