Was she influenced by GaGa? Sure. GaGa has put a spin on pop music that is popular and to stay current, singers/musicians/etc. have to go with it to stay relevant. Madonna is the prime example of this. She went with 80s pop....dabbled in more Sheryl Crow type music when that was popular....got back into dance pop once Britney became famous, etc. Inspired/Influenced by? Sure. Copied? NO!
CS - if the hair-piece you are talking about is the big fluffy wig thing, Christina wore something similar shortly after the Lady Marmalade video. She even wore it to an awards show, which pre-dates GaGa by a few years.
Again, nothing in Christina's album is a direct rip off of what's on GaGa's album. Nothing at all.
"They're eating her and then they're going to eat me. OH MY GOOOOOOOOOOOOOOOOOD!!!!" -Troll 2