Slap her with a brush & challenge her to a duel

And move

I usually dislike this joke, but damn it was a funny thing to imagine in this situation.

Yep, theft is always such a compliment.

Just like rape

No. They'll think it belongs to the roommate and OP won't get credit and will look like the art thief

"publicity" doesn't make up for theft nor does it pay the bills

How is that going to prevent someone from taking it?

because she would have actual proof the work is hers

It gives her an easier time getting it back if she contacts authorities, which is what OP should do if the roommate really won't return it. If someone picked up a few hundred dollars of yours and decided it was theirs you wouldn't let them get away with it; guard your paintings the same way, OP. If the roommate won't give it back, call the cops. You have the paint at least and the roommate can't have any proof that it's theirs.

Except, the roommate says it's a "gift", so signing it wouldn't do anything.

So if I went and stole someone's car and got caught, I could easily get off by saying" but...but it was a gift."

You're a special kind of stupid. A car has a title to it, it is registered to someone, it has to be SIGNED OVER to the new owner.

roommate thought it was a gift from someone else, so signing it would remove that issue. unless the roommate thought OP was secretly in love with her.... but that's a different problem

Ok, then what if you invited friends over and one od them took a wad of cash from you. If they say it was a gift, would that allow them to get away with it?

Like others have said before me OP, just sign your work, and then on the back write "Property of (insert your full name here)" that way there can be no possible confusion and in the event your roommate attempts to call the police or steal it again and you need to call the police, there will be no question as to whom the painting belongs to. Oh, and I'd gtfo ASAP lol sounds like your roommate is crazy.

I say while OP's room mate is sleeping, or maybe when she leaves for work, OP should proceed to sign the artwork to prove who's it is and then when the roommate gets back, go on to retrieve the painting. At least if authorities are called OP will have proof of who it belongs to with the signature.

Yes this would upset me and I would take authority over this situation. This is stealing, big problem. I do not like roommates who touch or take my stuff.