Well, I believe that even if she's a vampire, she will always thirst for human blood. So what if their enemies are dying without hope of surviving, is it ok for Jubilee to drink the blood and then kill it again so the enemy won't become a vampire?
How about if the enemy just died? Is it ok for Jubilee to drink the blood and kill it again so it won't turn into a vampire?
If you're Jubilee's fellow X-men member, and she asks permission from you, would you let her?