I saw! What about Xotomi finding her? It can't be all that unreasonable to be off planet and running into someone who might be seeking direction or a change.
Well everyone got dropped from the mandalorians. They're indie groups now, so you'd join one of the clan groups, as oppposed to the whole faction. Beyond that, you're more than welcome to join the Rebels, but you'll have to make sure the story suits - as the Mandalorians were a part of the attack that crippled the galactic alliance, from which many of the members of the faction were a part of.
You're more than welcome to apply, but if the story don't make sense, I won't be able to admit him into the Rebels, though.