AITA for not paying for my sister's wedding because she didn't invite my boyfriend who she knows I was planning on marrying?

I (30/F) have been in a relationship with my boyfriend (33/M) for 3 years. I've know for the majority of that time that I want to marry him. He's also indicated that he wants to marry me. The problem is our family. We both come from what I guess you'd describe as traditional families who don't approve of us dating. My parents and siblings haven't met my boyfriend yet. His family also doesn't know about me.<br><br>My sister (35/F) is the only person in my family who knows about my boyfriend. She's sort of the link between my family and me, in the sense that she keeps my family updated on my life. For example, when I got a new job she was the one who informed my parents and other siblings. She also keeps me updated on what's happening with my family. I don't talk to my family often, as it's very difficult and uncomfortable for me. The only time I see them is during holidays and birthdays. I don't like talking to them because that would mean I have to lie, which I've done in the past. I feel very guilty when I lie to them.<br><br>Last week my sister contacted me and told me that she's going to marry her long term boyfriend (8 years). I was surprised by this because I thought she'd have told me sooner. I asked her why she didn't tell me and she said she was scared I'd tell my parents. I asked her what she means and she said that she's worried I'd tell them about her fiancé's background. I didn't know what she meant so I asked her to explain. She then told me that her fiancé is from a different culture/ethnicity/religion. I think part of the reason why my parents don't want me to date my boyfriend is because of our cultural and religious differences. I didn't say anything about that because I don't really care about her fiancé's background. I then asked her if she's going to tell our parents about her fiancé's background. She said she hadn't made up her mind yet and was leaning towards not telling them. I asked her how she was going to do that considering they're the parents and the wedding is in our country. She then told me that our family won't be invited to the wedding. I was surprised by this because I thought our family would be there as her fiancé's family will be there.<br><br>A few days later my sister contacted me again and told me that she needed money to pay for her wedding. She said she wanted to keep it small, just her and her fiancé, an officiant, and the witnesses. I was a little confused because I thought she told me her fiancé's family would be there. She said they wouldn't be able to come as they live in a different country. I thought there was something strange about the whole thing but didn't want to question her about it. I told her I wasn't comfortable giving her money for her wedding when our family wasn't invited. I also told her that I had no proof that she was really going to use the money for her wedding considering our family wasn't invited. She said she didn't have any proof but that she needed the money. I told her I couldn't give her any money. She then said I was selfish and that she was my only family. I told her I wasn't comfortable giving her money when our family wasn't invited. I then asked her why I had to give her money for her wedding. She said it's because she's my sister and it's what family does. I told her I wasn't comfortable doing that. I then asked her if she was willing to invite my boyfriend. She said no. I then told her that since she wasn't going to invite my boyfriend then I wasn't going to give her money. She got angry and called me selfish and said I didn't love her. I only love myself. She then hung up.<br><br>She then contacted me again a week later and told me she was going to get married in 2 months. I asked her who was going to be there and she said it would be her fiancé family, her friends, and her friends' families. I asked her why our family wasn't invited. She said our family wasn't important to her and that she didn't need them there. I told her that meant she didn't need money from me either since I'm part of the family she doesn't consider important. She didn't say anything. I then asked her again if she was willing to invite my boyfriend. She said no. I then told her I wasn't going to give her money. She got angry again and called me selfish. I then told her I was selfish because she was being selfish too by not inviting my boyfriend. She didn't say anything and just hung up.<br><br>I feel like I'm being punished for something I didn't do. I didn't do anything wrong to my sister. All I want is for her too accept the fact that I'm in a relationship. I'm not asking her to like my boyfriend or be friends with him. I'm just asking her to accept him as someone I plan on marrying. She's been doing this for years and I feel like it's not fair to me.<br><br>AITA for not wanting to pay for my sister's wedding when she didn't invite my boyfriend?