I told his girlfriend

So ya’ll I might have made a mistake. Today I borrowed my exes car, and found a pair of womens shoes in the backseat. I confronted him and asked if he’s seeing someone and he said yes, he has for a month now. Normally I wouldn’t care but there’s still feeling because he tells me all the time that he loves me and we’re still sleeping together once or twice a week. Ya’llllll I took a sharpie and wrote on the bottom of her shoes “sorry babe but your bf is still sleeping with me”. I know this probably wasn’t the right move and really immature… I realize that now but I was mad and I let emotions take over. I know he’s going to flip when he finds out I did that and I really wish I hadn’t. Was any part of me right to tell her?

///whoa I think some people are confused. I wrote the note on the BOTTOM of the sandal, the part that touches the ground. It’ll rub off after a few wears. I couldn’t put a note in them and I had no other way of making sure he didn’t see the message. And I’m not mad at the girl AT ALLLL. I’m mad at the guy. I thought we were both single, just being friends with benefits and he MADE me the other woman without me even knowing. I wanted to tell the girl because I would 100000% want to know if it was me. Especially since we weren’t using condoms, we all need to be tested. Yes I feel badly about how I did it but it wasn’t to hurt her, it was to hurt his cheating ass.