mother problems (long post)

So ok . Let me try to explain . I have a older sister who has two kids . She got pregnant at 16 , and my mother who has always been controlling and quick to take over things quickly "took over" my sisters pregnancy. Forcing herself into every appointment , making decisions , the list goes on . Ok so I understand , my sister was young and I guess that semi makes a difference in the situation . I'm will be 22 weeks pregnant tomorrow and also just turned 22 , and this is my third pregnancy but my first child . Well up to this point , I've been pretty good at standing my grounds at what I want done during my pregnancy . She hasn't been to one appointment tho she wines and complains , and it's not me being mean y'all just don't know my mother . 🙄 ok so this is my issue right now , when my sister had my niece and nephew , my mother over stepped her boundaries again and took my niece and nephews foot prints and got it tattoo'd on her leg . Seems harmless , but my sister didn't really care for it and it seems more like a tattoo the mother or father would get . My sister has been upset about it from day one but she didn't stand up for herself . My mom made the comment today to my younger brother to tell the tattoo artist we use (he was going get a tattoo today) that she would be in soon (around end of March) for more footprint tattoos as she's having another grandchild . I mentioned it to my boyfriend and we both agreed that she can obviously get something for Carson , but not his feet print . But how do I tell her ? I know she already feels like I'm being mean and not letting her be apart of this pregnancy , but I don't want to be upset forever if I don't stand up for myself . I just don't know what to do . And any advice would help . 😖😖😖😖😖