"Heart of the Team?" Heck, no.
Jubilee's Yellow power is titled that. If I recall from the comics, other characters and most fans hated her from the start. She was an annoying, snarky brat who got attached to Wolverine's solo title just so he couldn't get too bloody for the comics code. When she was forced to join the younger groups, she called them the "X-babies" and none of the others liked her. In retrospect, sure. She's a classic X-character, and eventually fit in.
Was there something in the TV cartoon series(es) where she became the "heart of the team"? 'Cause if so, I missed it.
I just keep seeing it flashing across the screen on a banner during this PvP, and it's finally gotten to me...