I would vote for a slight cooling off of your relationship with Bree.
Don't get frosty--just don't be quite as friendly. Be pleasant, but don't be chummy. Don't seek her out anymore outside of the squad.
This is a good practice for you, for later. In how to "be professional" and not let the personal interfere with work.
And then just model "proper behavior" for all the girls on the squad.
In fact, this is what I think the major role of a team captain is--to serve as an example in terms of decorum, interpersonal relationships, dedication to the squad, etc. (I'd say, "how would a grownup behave in this situation?" but not only is that patronizing, it's also unhelpful, bcs plenty of grownups behave badly. So instead I'll suggest for you the role model *I* have in my own head: "channel your inner daycare worker." In other words, "keep calm and carry on." Be calm, be pleasant, don't stoop to finger-pointing or justifying.)
Also, give the other girls room to not have to be involved in the drama. Be dedicated to insisting on a "drama free" zone around you, which will also let the OTHER girls ignore this until it blows over.
Another reason why not to get into it: The more you actually *address* this, the more you send a subtle message that she might be right, and that you are reacting because you're defensive, and that you're defensive because she's right.
She's being immature and petty; she's letting her personal disappointment lead her into unprofessional behavior. So *you* model for *her* (and for everyone else) how it is that she *SHOULD* have acted when she found out.