I live with my fiancee and we share all of our expenses, car, bank accounts, etc. I'm at the max I can deduct in student loan interest, can she claim the rest of it under her taxes? Its paid out of our joint checking, which she has direct deposit to.
No. Even if you were married, she (and you, jointly) still could not claim anything above $2500 for the two of you combined (even if she separately had interest) - the deduction is $2500 max regardless of married or single. See Intuit's very detailed help page for more details.
If you were her dependent (and she claimed you as such), she could claim the deduction but not you; but that's only if you were her dependent (and again, the max in total would still be $2500).
Further, the details include that the loan must have been taken out in your name, and the student must be you, your spouse (not fiancée, sorry) or dependent. As such, only one person (or one married couple) is ever eligible to deduct student loan interest from a particular loan.