Current girlfriend hanging with ex girlfriend?

My girlfriend and i have been together for over 2 years now and we also live together. She has a wonderful son who's almost 3. My problem is we also live with her ex girlfriend for over 2 years. I understand that they has this child together and they both want to have him in their lives and im not asking for that to change. But i cant stand that the 2 of them spend every moment possible with each other going to bars hanging out so on and so forth. When i brought it up to my girlfriend it bothered they spent so much time together she said they are friends and that im always right there. Which is true but the problem is even though im right there im cooking or cleaning or they are talking about something they watched together in spanish (which i don't speak) I have tried to get her to move out to a house just a few blocks away but she always says no. My girlfriend owns the place where we stay but her ex girlfriend gets the only say in everything. When my girlfriend bought me a dog the ex said it had to stay in a cage or outside but it wont be running around in the house. She wont even let my brother come over and visit cause she says there's no room and she doesn't want my brother her. The funny thing about this is her 2 twin sister and her 18 year old brother live with us also which make a grand total of 7 people living in a two bedroom trailer. I agree threes not a lot of space but her family could go stay at there house just 15 Min's from here. She has even gone so far as to tell me and my girlfriend that if we want to be intimate with each in our room with the door closed we have to go some where else cause its not fair that we do anything while shes living there. So i guess my question is am i over reacting is it perfectly normally to let your girlfriends ex run everything? We Split the bills i do all the cooking and jayden(the son) is all of our sons. Let it go or walk away?