Furious Ashley MCMullen has revealed she inked Demi for free in 2011 - and then had to clean up after her famous client left a mess in her parlour restroom.

And, after learning Lovato had covered up the tattoo she likened to a vagina earlier this month (Apr15), the artist was far from happy.

In an angry Instagram blast, she writes, "Thanks for getting the tattoo covered up I did for free that you specifically asked for. Not to mention you didn't even have the courtesy to offer me any money in the first place.

"You p**sed all over our toilet seat and you made a fool of yourself. What a shame that people look up to you. The tattoo you covered it with kinda sucks too. Looks like you might forever be a goon."

MCMullen later added, "It's a really nice example to people your (sic) setting saying to not do drugs, but honestly you were acting like a full time slob... For the record, I'll be posting my story until I get an apology. You never even gave me a shout out after I dealt with your drunk a**."

Lovato covered up the vulgar lips tattoo with a new image of a rose.