Thankyou so much for your thoughts and experiences regarding this situation.
Loca had her vet appointment yesterday, and the vet suspected her to be closer to six months old, though he said she certainly does have a small build.
She was in fact pregnant :sad:; and due to her age and tiny build the vet encouraged us to spay her regardless.
We had her spayed and are waiting until we can bring her home, most likely tomorrow.
Other than that, Loca is extremley healthy and very happy. We are all glad she will be okay.
Thanks again for talking me through this everyone, I really appreciate it!