Daughter is mad against us!

Hi guys!

I am 22 and my girlfriend is 32, she has a 15 y-o daughter who agreed for us to be in relationship and we have a great relationship overall! The problem comes with our sex life.. My girlfriend and I are having sex quite often, which is normal for adults and we are trying to make no noise and be respectful as much as we can, but we live in a small house and our rooms are quite close so sometime we are heard. The problem is not that, but more the reaction of her 15 y-o daughter who seems to have the need to adress it everytime it happens which is quite annoying... For a while she was even listenning on the wall so then she could tell us that we are disgusting and annoying.. sometime she was knocking at the door randomly just to annoy us etc.. She seems to be very upset and angry about our sex life and I was wondering why she is angry against something totally normal..
Thanks for your help!

Why do you think she is angry, or why she is listening?

Perhaps she genuinely is bothered by it. I wouldn't want to hear my mother moaning either. She is a minor, at the end of the day you need to cater to her needs, not your own.

It is possible that she is jealous. After all, you are closer to her age than you are to her mother's age.