This fight was long in coming, but I just read one of those Internet question thingies where some interested person asked who would win if Jubilee and Cassandra Cain/Batgirl/Black Bat fought. The consensus was Cass would win, although one person commented, "Jubilee, hands down." That person must be huffing ground-up Marvel comics for an expensive high because that answer is hallucinatory at best.
As a fan of both characters, I'd hope Cass and Jubilee would simply team up and fight some other person for some desperate, comic book-y reason. But one of the things we do here (the royal "we," since this is a one idiot operation) is pit Cass against various characters from comics and other pop culture media entities. We can imagine their initial encounter as one of those clichéd comic book mix-ups where two heroes meet for the first time, fight, then unite against a common foe, or two (one from each's standard rogue's gallery), but the fight is the thing here, not the overall story.
So here's how things would go down if these two tangled.
It wouldn't last very long. While Jubilee has Danger Room combat training and real world experience, there's no version of the character who can match Cass in hand-to-hand fighting. Cass is simply one of the top two or three unarmed combatants in the world, and possibly at the same level with weapons. Jubilee is, charitably put, not. Unless a psychic teammate alerted Jubilee to Cass' presence, Cass would strike from the shadows and knock Jubilee out before the poor girl could ever use her mutant fireworks power. Over before it even begins.
And even if Cass should miss with her first attack (she wouldn't unless Jubilee has some major help), it wouldn't take her long to figure out Jubilee's X-training patterns and dodge the little plasma balls tossed her way. Jubilee would be faced with the choice of grappling hand-to-hand with Cass (certain failure) or using her powers in much more violent and destructive way (really her only chance, but one she would find unappealing). Operating under her ordinary moral constraints, Jubilee might dazzle Cass' eyes or even stun her for a moment's respite, but even so, this fight would last at most a minute or two.
That's classic Jubilee. Vampire Jubilee would be another story. I'm not certain just how many of the traditional vampire powers and weaknesses Marvel uses in its continuity, but if they use the familiar ones, vampire Jubilee would be largely impervious to most of Cass' martial arts attacks-- save those involving wooden stake strikes directly to the heart. As vampires possess speed and strength in excess of most mortals (Superman-types excluded), Cass would have to be well-prepared in advance with vampire-specific weaponry. It's doubtful Cass would carry holy water, garlic, stakes or religious symbols on her person under ordinary circumstances. Vampires also possess various transformative abilities, one of which renders them as insubstantial as a mist or fog. Kind of hard to fight mists and fogs.
I can see this fight as having more than one possible outcome. Under these circumstances, Cass would find herself outmatched and forced to use her smarts to out-think and therefore defeat Jubilee. Jubilee, however, is a pretty smart cookie and doing so would prove easier said than done. In this case, the fight goes to Jubilee barring some intervening circumstances-- nearness of dawn, for example, or whether or not Cass knew in advance her opponent was a vampire. In either of those cases, Cass would win by exploiting Jubilee's vampiric weaknesses in much the same way people of lesser ability manage in multiple stories to destroy even the Lord of Vampires himself, Count Dracula. And there's no way Jubilee is even close to being in Dracula's weight class.