Can she really sue him if she shared her account with him? Legally, it's his money too. Not saying what he did was responsible in the least, but it's a risk that she apparently took willingly.

how do you know the money was in her account ? she could have had it put away in her house.

who keeps thousands of dollars in a glass jar these days...?

old people

Legally, her money is her money and his is his. They're not married, so even though it's in a joint account, it isn't community property (or whatever non-community property states have that basically works out the same most of the time). If she has pay stubs, deposit slips, or some other evidence to substantiate the money she earned, she could be able to sue him and prove the amount in the account that was hers. Now if she went to a glorified mediator such as Judge Judy, she'd likely get the result you're imagining, plus a lecture about how stupid it is to share access to a bank account to a guy who hasn't put a ring on it. If she went to a court that actually had to apply the law, she'd have a fair shot at getting at least some of the cost of the bike back.

While i agree holidays are a waste of money and some thing like a bike is a better way to spend money, it was OP's money so it doesn't matter.