Could Gajeel eat her? ...just saying.
Even if that is true, baby 5 is still pretty low level in the OP world and was taken out by the weaker members of the Strawhat Crew. Gajeel on the other hand is almost one of the top tier in the FT world which includes people like Laxus, Erza, Natsu etc. and they have all shown near town/city buster feats. I've posted speed feats shown by Erza and Laxus is some of my older posts and they're all much more impressive than anything shown by a relatively weak pirate like Baby 5.
Gajeel is much too powerful for her.
Edit: Also no one on team FT ever loses. This is fact. Only someone on team FT can beat someone of FT.