Best friend in new relationship, now we barely spend time together

Long story short, me and my best friend have been going through a rough patch in our friendship for the first time tbh. We got put in halls together at uni in first year and then in second year we lived in a 2 bed flat so we’ve naturally gotten really close by sharing routines, spontaneous plans and day to day life. We’re now going into third year and are still living together but with a few others. Anyway 2 months ago I had an important meeting and needed her help, she turned up 2 hours late to a 3 hour meeting and said it was because she was playing tennis with the guy she liked (who is now her boyfriend) They already played countless times that week and I was just so hurt by it because it was so unlike her, she was normally reliable and trustworthy. Later we talked about it, she said she “knew I’d be upset but stayed anyway”…I forgave her but our friendship hasn’t been the same since. We’ve had countless conversations and have made mistakes on both sides trying to navigate this while also living together. Anyway over time she’s done other things that have contributed to my hurt and I’ve felt like the repair of the friendship has mostly been on me, which feels unfair considering this started with her mistake. When our friendship needed the most repair she was suggesting a coffee or a walk once a week, which felt unnatural since we live together and practically shared routines, going from that to then suddenly barely seeing her felt so strange. During the last week of our tenancy I communicated the prolonged hurt on my side, she listened and apologised. That last week felt somewhat normal, we’d have spontaneous plans between packing and moving stuff, and I thought we were finally okay. Now we’ve moved, she’s back to always being with her boyfriend and by extension his friend group, we’re in our third year house now under the same roof and I rarely see her, we maybe hang out properly once a week. She’ll be leaving soon for summer and I just feel like we’re not even gonna be close at all when she comes back. I know friendships change when relationships happen, I kind of expected it but it still hurts to have lost the sense of safety within our friendship at the same time, I’ve felt really alone in that feeling because she doesn’t seem to really care that we’re not close anymore. How do you handle it when this happens? It’s her first relationship and they’re only a few months in but it’s been hard to adjust to.