Is ok to be feeling this way? Help?

My partner is 24 years old, he's been living with his nan since he was little. He's an only child and his mom has a life with a new fella. So his nan has been a massive role. So a few months ago my partner and I had an argument which was sorted however his nan had done something to upset him and them two had an argument. Since then I'm not welcome to the house (I did live with him and his nan) and I'm told that it's all my fault he was like that on that day. I've finally made my partner realise he's too old to be living with her and needs some independence. We've been house hunting but she's now so rude to me and makes me feel uncomfortable when visiting. She treats him like a baby and says things like "he won't leave his nanny, will you?" Like he's 4. Thing is he won't ever stick up for me and tell her she's wrong for being that way towards me? How should I go about this?