She had just gone through a breakup and wound up bouncing her emotions off me to have someone to support her... .
It's really hard to coach anyone on these things because it is very much a matter of the heart.
Forgetting about her for a minute... .rebound relationships are notorious for littering the landscape with the carnage of loving rebound partners. Generally, rebounds are rehabilitating relationships. When someone breaks up, there is a huge void to fill. A rebound fills that. There are often complex emotions if someone broke-up (guilt) or was spurned (grief) and a new suitor is a great antidote for these feelings. In short, the rebuild is often a healing bridge from one relationship to the next phase of life.
The thing about rebounds, is that there is this fast attraction, quick emotional intimacy, and high. When the person heal, the relationship often unexpectedly end or breaks down.
How does that play here and is there a way to predict if the is something more than a rebound? I don't have an answer to either question. I have been in two rebounds in my life. They were incredible and then ended unexpectedly. I swore, after the first one, to never do it again. I encountered another (a decade later) and I thought I had a handle on it, but it ran the same course. Both times, the person made a very substantial life change at the end of the relationship... .and did the "single time" and recovery that they should have done at the end of their relationship. The relationship I was in was a phase in their recovery.
To the re-bounder, this can really soften the blow and the loneliness that happens at the end of a meaningful relationship. The the person involved, it can be confusing, sudden, painful, and a setback.
Be careful. If you look on dating sites, many people won't date others who are divorcing or recently divorced or who haven't had a relationship since their divorce - those are people who were crushed by a rebound or two or watched someone else crushed by a rebound.