I'm thinking of lying to my ex-gf when I get my tax return because she wants half
Why do you want to hide your money from your ex?
Because I don't want to share everything with her.
You're right about not sharing the refund, but unless you had a legal bond via marriage or a business, she has no right to one dime of the refund. No worries on this issue.
Well I am going to say I paid for a lot of the bills and buy her things.
I'm sure she'd appreciate that. That way, you can control how it's spent and keep her oblivious at the same time.