Ex Gave Me A Dog We Once Shared Together, Almost 2 Years Later Wants The Dog Back

Hey all, just a quick question - my ex partner and I lived together and shared a dog for a few years, things got messy and I left and got my own place etc. almost a year after being separated she texts me offering me our old dog because she could not keep her and already had to rehome other pets. I ended up taking the dog and have had her for almost a few years now, she’s a registered ESA for my new partners emotional health. I have the screenshots where my ex partner had offered to surrender the dog to me and I accepted and have had her since. She’s also periodically messaged me asking for the dog back which I’ve declined bc I’ve grown reattached to the dog and she has a good home environment. I currently got a summons in the mail with my ex partner claiming I’ve been unjustly withholding my dog and I either need to surrender the dog or give her $1500. Will my screenshots proving she surrendered the dog to me, the dog being on a recurring lease for a few years and being registered be enough to dispute the claim and keep her/not lose 1500?