Advice please!!

I’m not a parent but i’m coming to you guys for advice. This is going to be a long one so get ready. After searching the internet for hours I feel bad about how I feel right now, I know that a mother has the say in who should be able to hold her baby but I just want to explain my situation. Please read everything before you comment because I just need advice. I want to be able to have a conversation with her without her thinking i’m getting angry at her or that my feeling are hurt but it’s hard because my feelings are hurt. So here it is I guess.

Before my sister-in-law had her baby we would talk all the time about how she was excited for me to have a good relationship with my niece because she doesnt ever get to see her nieces and nephews and she didn’t want that for her daughter. The first time her and my brother came over to my parents house with my niece I was able to hold her and love on her, she was so tiny and I fell in love immediately. The next time they visited I asked to hold her about an hour after they arrived at the house and my sister-in-law told me that she wanted to feed her first and change her diaper, I understood and didn’t think much of it. I didn’t ask again to hold her again because I guess it just slipped my mind. Every time after they visited and I would try to hold her she would say she had to feed her or she would go change her or she would put her down for a nap. It didn’t matter if she fed her literally 5 minutes before or if she changed her literally right before I asked. So I told my mom how I was feeling because it was starting to really upset me. She asked me if I wanted her to talk to my brother about it and I shot her down so fast, I didn’t want my brother to tell my sister-in-law how I was feeling and have her say I was looking into things too hard or something along those lines. After that I just stopped coming out of my room when they would come to visit, I would tell my mom I didn’t feel good and I just wanted to stay in my room. They came over today and I told my mom once again that I just wanted to stay in my room. I think that was the final straw for her or something because after they left she came into my room and told me how she pulled my brother to the side and told him how I was feeling. My brother said that it wasn’t that my Sister-in-law didn’t want me around her it was that she was telling him that I would wake my niece up when she was sleeping. My mom flat out said that was a lie and how 3 visits before I had told her how I was feeling and how I put it to the test the next time they visited, and once again my sister-in-law walked out of the room to feed her even though she had just finished eating. I mean like not once have I asked to hold her while she’s asleep or after she just woke up, not even before she’s about to go down for a nap like I can respect that she needs to be able to take naps. My brother got extremely angry when my mom told him all of this because my sister in law had been lying to him about this, he had no clue what was actually going on. He told my mom that he was just going to go inside and bring my niece into my room so that I could spend time with her. My mom told him not to do that because I had asked her not to say anything to him.