Is she in a rebound relationship and will it last?

My ex of 4 years has just broken up with me about 3 weeks ago and is already in a new relationship with a guy she crushed on when she was a teenager she's 30 now. She said she just can't commit to me right now and wants to be free. This new guy is a total loser who lives with his grandparents, is a registered drug offender with no job and I know he will just lie to her and cheat on her. she always goes to these kinds of guys when we have problems but this time she doesn't seem to want to fix it with me. She says he's a nice guy and she's happy with him and that it's not just a fling and might get serious. she's already texted me crying that he ignored her for a day but then he answered and said he was busy so she is afraid i will be right about him but still is insistent on trying it with him and she's going to ruin what we have. She wants me to be her friend because I have stood by her for years long before we dated and she has children from before me that see me as dad and that's fine with me I love them and she wants me around for them. She has kinda rubbed it in my face that she's happy with him and this basically has all the signs of a rebound. He got with just hours after dumping his ex, she always told me she wanted us to be a complete family someday but is now throwing it all away for a middle school crush so my question is, is this a classic rebound that will fail soon cause I know this guy is trash and should i remain in contact with her as well as her children or just stop talking to her unless it's about them? which will be more affective in convincing her I am the one for her keep coming around in hopes the guy will get frustrated and leave? or try and make her miss me by not seeing her. I'm pretty sure the guy isn't serious about her just using her for sex his ex complained he was a hoe chaser on her Facebook.
Is she in a rebound relationship and will it last?
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