NTA

I usually instinctively side with the DIL/SIL (husband's wife) for these Reddit relationship AITA questions, probably because I'm a married woman and can imagine myself in the DIL's shoes. But in this case, I'm actually siding with your mom. I'm sure your mom is no angel, but she might be seeing something in your GF that you can't see (yet). She might know that your GF is not good for you and that your relationship is doomed.

Even if your mom was awful, your girlfriend could just avoid her. I don't think you'd force her to socialize with your mom? But instead, your girlfriend goes to your mom's house and acts like a petty one-upping drama queen in her own home? Not cool. Then she calls you spineless? Unbelievable.

I personally can't imagine dating someone this immature, petty, graceless, and tactless. Let alone marrying them.