I feel that Jubilee has always had a desire to remain moralistic and 'good,' when it came to the use of her powers. Even when she was a mutant, her ability to detonate matter at an atomic level was never fully played out... as her conscience wouldn't allow her to take a human life. Instead, she found creative ways to blast away at the bad guys without hurting them.
Now that she is a vampire, the same can be said for her in regards to her abilities. She started off high on angst and temptation as a vampire, but with the proper guidance and treatment, finally decided that she still never wanted to take a human life. Instead, I believe she restricts herself to an animal blood diet, as well as transfusions of blood from Wolverine and/or X-23. However, it has been awhile since we have seen this on panel. I actually feel that the writers are trying to ignore much of her vampirism due to either laziness or else the fact that they adore her classic traits so much more.