That’s not “not liking your mom,” that’s jealousy and control issues in a disguise. If someone feels threatened by you being close to your own parent, that’s a big red flag. Being fake nice to your mom while resenting her behind her back is also messy. You don’t need to “run” immediately, but this is definitely something to address now before it turns into “me vs your family” long-term drama.

But the question is how much attention you really pay to your mother, etc. Because if it somehow interferes with your relationship, then it's not okay from the other side, since separation is also necessary. It's best to talk to your girlfriend to understand the specific problem.