I'm well aware this is a website for women, but as a guy myself I can say guys can be very immature about things.. So I need a woman's point of view even better a mother's point of view.. I apologize for any inconvenience in advance.

The problem is that I have been dating my g/f for one year and four months.. Her father found out I existed a couple of months ago, I thought that was the least because her mother loved me.. [I believe] her mother is actually one of the main reasons I still see her and am able to talk to her (My g/f).. I havent done anything that I can think of to make her upset or anything of the sort but she has changed and seems distant recently.. And i'm always on my best behavior and never disrespect neither her or her daughter..

What could be the cause of this?