<human>: I'm 22 graduating college in two weeks and my parents and sisters are coming down for the ceremony. I currently live with my girlfriend (23) of 2.5 years, and my mom asked if she not come to dinner with us on Saturday because it will be the first time my family will be together as a whole and she wanted just the five of us to have a nice sit down dinner. 

My girlfriend got very upset and now does not like my mother, but she would be going to lunch with us after my graduation. She shit talked my mom a little because she was mad and then got mad when I defended my mom seeing where she is coming from since were all grown up and won't be home all together again for maybe a year or so.

My girlfriend believes that my mom does not want her as part of the family or see her as part of it. I see it differently obviously and do not think I am wrong for siding with my mom because I see her point of view and understand it, while I think that my girlfriend is acting like a child

Am I in the wrong for "siding" with my mom, or am I in the wrong for not siding with my girlfriend

Can you summarize the given text in a few sentences?
<bot>: Mom does not want girlfriend to have dinner with us the day before my graduation and my girlfriend got furious, sided with mom, caused a lot of tension.