My friend has lied to me, avoided, and starting to ignore me ever since she got her new boyfriend, what to do?

So my best friend just got a new boyfriend the week she dumped her first one, and he’s been sleeping over her room every night since. (about half a year now) I think he’s a rebound guy because she never had feelings for him before, but knew he liked her so she decided to use him after her break up, but now she’s trying to convince herself she loves him to make herself feel less..easy, I suppose. I’ve looked up what to do in these situations, when a best friend spends all her time with her boyfriend—and I’ve taken that advice and asked her to hang out and told her I missed her..and she would always say, “oh, sorry I miss you too, I’ve just been too busy”. Which is not true because she spends all her time with him playing games, watching tv, shopping, etc. Sigh. She’s lied to me about being able to hang out, and now has stopped talking to me completely. She doesn’t say anything to me unless I say hi to her. I’m hurt and feel like..if she doesn’t care about our friendship, should I bother trying anymore? Every time she has a problem she comes to me for help. Emotional problems, relationship problems, etc. Am I just being a tool? I feel like it’s so unfair to me, but whenever we do hang out together it feels ok again. But then she’ll return to her usual self and start ignoring me again once the problem is over. How do I deal with this kind of best friend? I don’t even think I should call her that anymore =/