This is a top tier ally.

She costs very little, and she basically delivers 6 damage on the turn she comes into play.

Certainly, you may not be able to attack with Jubilee and Wolverine on the same turn. But if so, that means you played her to chump block out the gate. And you should avoid playing Jubilee if you aren't able to attack with both her and Wolverine, otherwise you're leaving damage on the table.

What's extra awesome is that there are cards to make paying X-Men cheaper, and plenty of leadership cards that boost ally stats and ready them.

You could easily build a deck around just getting Jubilee out with her bonus to take out a problematic minion, then bring her back the next round to throw down on the Villain.

Meanwhile, Wolverine ALSO gains the bonus. What an incredible intrinsic ally.