Ex gf is seemingly having sex with, and in love with a rebound a month and a half after our relationship ended?

[RaNdOm]

My ex and I dated for four and a half years. I just learned that, now one month (could have been even sooner) after we broke up she is already seeing someone else.

She publicly goes everywhere with him on social media, and a close friend of mine saw conversations of hers where she said stuff like, "I miss you so much", "im so into you," etc. She also talks with this guy about how great their sex is, etc. It seems like she moved on so soon and entered a serious, sexual relationship so quickly. It hurts because it makes me feel like she either knew this guy while we dated or just didn't care about me at all.

I know I shouldn't contact her at all about this. I don't need advice on that, even though i want to because she always said she needed to "learn how to be alone" and now she's already banging some other dude and intermingling their families.

Do you think this is a rebound relationship, and if so, has anyone else felt that way about a rebound only to later learn that they really didn't like the person that much? I just need some satisfaction in knowing that she's hiding the pain of our break up with this and doesn't like this guy as much as it seems and will eventually regret this. Any thoughts?