I would argue that the songs she writes are juvenile and poorly written anyway. Did you see that interview after her "Party in the USA" song in which she couldn't name a single Jay-Z song?
I'd like to point out that anyone on these forums could write a song like party in the USA without any training whatsoever. Seriously. It's been a long time since I have heard it, so perhaps I am mistaken, but if memory serves, there are no chords in that song. I mean, what the smurf? Who in their right mind thinks "I'm gonna write a song without any harmony. There will just be a clapping and a drum beat and 'singing'"

Furthermore, have you ever heard her sing? I've heard her try to sing, but actual singing? She seems to lack that ability unless auto tune comes to her aid.

That said, party in the USA is the only song of hers that I actually know, so I could have a biased view. However, the sheer popularity that song has achieved speaks volumes about what she is capable of. Don't you think if she were a better songwriter she'd have more popular songs than this one?