How to remove lush henna hair dye?

Does anyone know how to remove lush henna dye? My hair was platinum blonde at the roots and blonde everywhere else with a slight orange-ish to it. Not a big color difference. I used the lush henna dye and it looks absolutely amazing on my roots, it’s the exact color I needed. (Even professionals have failed in the past to give me this exact shade!) but everywhere else it just looks stupid. Some parts are still blonde (which I obviously missed) and I had another block of dye to touch up the places I miss. But the places it did dye it just looks dark blonde. Which is weird because I’ve seen people on YouTube with hair darker than mine and it turn out great. I want to get it out of my hair so eventually I can go to a salon to get all platinum hair and once I have that, use the henna again since it does give me the shade I need and it’s healthy. I just can’t figure out how to get it out of my hair.

Can I bleach it out? (I know bleach ruins your hair.)

I heard olive oil makes it come out?

My hair grows very very slowly. It would take years to grow it out so I don’t really wanna do that