I've been friends with this person, let's call her Friend 1, for 15 years. Up until the past year or so I would've called Friend 1 my best friend - she was a bridesmaid at my wedding, we've travelled together and would message each other every day. I noticed that Friend 1 has become increasingly close to Friend 2, who I'm also close friends with, but I didn't really think much of it because obviously it's not as if I mind if she has other friends. We would often do things with all three of us but more and more Friend 1 and Friend 2 would do things without me. Again fine, but Friend 1 started to drop off contact with me e.g be very slow to respond to messages and constantly be hanging out with Friend 2.
About a year ago I moved abroad and while Friend 1 initially was really good about keeping in touch, she's now become very hot and cold. Sometimes I get a bunch of messages and sometimes days and days will pass without any response to a message. We're on several WhatsApp groups together which she's constantly sending messages on so I know that it's not that she's really busy. Also, she was previously in contact with me so often (a few messages a day) that it's very noticeable when it drops off.
At first I tried to keep initiating but after repeated delays in replying I said to her that she doesn't need to feel obliged to keep in touch and that I wouldn't want it to become a chore. She replied saying that of course it wasn't, that she really values my friendship etc. and for a while she'd initiate more, but again contact has become really on and off. It feels very much like she's phasing me out and has almost 'replaced' me with Friend 2.
So what do I do now? Do I just not bother anymore? It's hard because we were such close friends, like sisters really, and now I feel that she's just lost interest and forgotten about me.