How do I (27M) tell the difference between rebound feelings and actual interest in another girl (28F)?

I somewhat recently (3ish months) got out of a LTR (6 years) which was one of those situations where we tried to make it work for a year longer than we should have and it was a slow burn and fade of feelings. Emotionally, I had dealt with the loss of the relationship about 6 months prior to the end of it. By the end of the relationship, it was mostly dealing with the guilt of letting it go on for so long.

Therefore, I have been feeling interested in dating again as I have been emotionally missing that intimacy for probably 9-12 months, but due to being in the relationship until just 3 months ago I wasn’t independent and single. Now that I am, I have already found myself interested in dating and wanting that back again.

Bring in the new girl to the picture. Without going into too much detail or context that is unnecessary, she is the roommate and friend of my best friend’s girlfriend. I met her towards the end of my last relationship, she had recently moved in with the best friend’s girl (couple months before my relationship ended). She was also getting out of a LTR. Immediately I had an attraction to her, but never thought much of it or spent much time around her until more recently.

In the recent months since I have actually been single, I’ve been tagging along with best friend and their outings, which have included the new roommate. We have had a few conversations, made some jokes, there has been what I think is flirting (eye contact, smiles at each other, sitting near each other without the other closing themselves off, etc.). It seems easy for us to spend time with each other and talk. Given the few outings with her and more time spent, I am finding myself having genuine interest in her.

The part that I am having a hard time with is understanding the perspective I should have about this. Am I just finding this girl attractive because she is cute, confident, down to earth, and fun, while simultaneously being different from my ex, therefore I am fantasizing about what it would be like to have someone like this and having some rebound feelings? Or could this be a real attraction? Would it be ok for me to just ask her to go out the two of us to get to know each other and see if it is real? Or would that compromise the situation seeing that we have a bit of a friend group going right now?

Tl;Dr Recently out of a LTR, met a new girl as a part of a new friend group forming. I feel like I am attracted and interested in her, but confused if it is just rebound feelings and fantasies because of my ex or if it could possibly be real attraction.