If I were the Mom of that boy, I would want to know... if my son were being a jerk....
At this age, teens need to be accountable for their actions... .and parents need to monitor them... AND their online accounts/pages.
I would bring it up.
I would, make sure the parent's of that boy... KNOW he has a Facebook page... maybe they don't know? They obviously are not monitoring his online habits...
Then for you as a Mom with your daughter in this situation... its good you are talking with her about it. It is a real hard lesson... and hurt feelings and how people can be jerks... BUT that it is up to her to STILL be confident and to be proud of herself for who SHE is... and that other people's jerk behavior does NOT have to make "her" feel crappy. She can rise above it... and not become lowly like them.
Teach her that... that her sense of self-worth... is NOT contingent upon a boy. Because, as she progresses in life and relationships with guys... this will happen again. So... help her build a strong foundation about herself... her own identity... and self-confidence and the ability to navigate herself positively. And wisely....
Teens... are hurtful and gossip and bully and create drama. So, as you are doing... always make sure your daughter can come to you (and Dad) for any problems, concerns, any feelings or issues she has... so that she always has you as a sounding board... and as a rudder for her ship.
My Dad, always taught me as a girl... to be proud of myself, not a follower, and to always be who I am... and not to let boys trample on me. There is appropriate behavior and inappropriate behavior... which my Dad taught me... AND that, I as a girl, can speak up or be smarter about who I "let" into my friendship.
If a guy is a jerk... then take it as a lesson... and as a person, you are better off without them! They, the boy, should respect you... and not be a different person depending on who they have a crush on.
All the best,
Susan