Just compare the cost of living to what you got now.
Deduct any additional expenditures and project out as far into the future as this relationship will last.
If this additional expense doesn't bother you, live with her if she makes as much as you, otherwise don't.
The last proviso were it a consideration would not have been on me but her, so that wasn't the issue in my decisions, but I'd have to say it should be in yours.
LA sucks without knowing people. At 22, this isn't an intelligence level that could relate to your business unfortunately and that will negatively impact your trading unless you're trading with algorithms.