feeling replaced and forgotten

Hello. I have always been very close to my sister, throughout my entire life she has been my closest friend who i spent most of my time with. At the end of last year she got a boyfriend, and as much as seeing her in such a happy and healthy relationship makes me happy i can't help but feel lonely because the time we spend together has decreased a lot. She spends the weeks at her boyfriend's place and sometimes comes home for the weekend, if she comes together with him i feel really lonely because they will spend all the time together while i'm alone in my room and listen to them have a good time when i just wanted to spend some time with my sister. I feel that many things i used to do with her she now prefers to do with him. There have been moments when we have discussed on doing something together but then she ended up doing with him instead, like a movie i wanted to go see together but never saw in the end because she watched it with him instead. I feel like she doesn't even want to try and spend time with me now. I don't think she has even realized that i feel really lonely and distant from her, and i'm afraid of discussing it because i wouldn't want to ruin her happiness and make her feel bad. Has anyone else struggled with becoming distant with a close friend when they got into a relationship or had somewhat similar situations?