Brassy highlights on top of head before wedding!!

Hi all

I have naturally dark brown hair and after having a break from dying it for a couple of years, decided to have it highlighted. Anyway, I'm living in a new area so went to a hairdresser that lot of people had recommended and had won an award. The hairdresser said my hair was in really bad shape so cut about 4 inches off it (quite a surprise when she told me she'd only cut a maximum of an inch!) and said to come back in a couple of weeks and she'd highlight it.

I showed her around 8 photos of how it used to be so she'd have a relatively good idea of colour, and told her I definitely didn't want any brassy yellow or ginger colour going on (which has happened with a past hairdresser!) - she assured me it would all be fine.

Anyway, she used lightening powder as said this would be kinder to my hair. Once she'd taken the colour off, my hair looked really yellow/orange so she toned it. The bottom half of my hair has come out fine (not at all how I wanted it but objectively it looks ok) but the top half has on one side a bit of a large patch of very brassy yellow with an orange tint! This perhaps wouldn't look so bad if it was at least even, but the other side of the top of my head has thinner highlights so perhaps it's just as brassy but not really noticeable when mixed with my brown hair. It also looks weird as she's left about a centimeter gap between my scalp and the colour (presumably as to not damage the roots but if that's the case, I wish she'd told me she was going to do that!).

She said I could come back and she'd fix the top part for free (the yellowy/orangey colour) but I've been back twice since then and both times she's been closed. I have a wedding on Friday and I'm wearing a bright banana yellow dress so having this brassy strawberry blonde on top looks absolutely awful!!

Is there anything I can do myself to try and improve this? To be honest, I'm not sure if I even trust her to work on my hair again. Ideally, I'd want to try and tone down that big strawberry blonde patch or at least break it up with a bit of my natural brown! I've tried two local hairdressers but one was fully booked and the other didn't really understand what I was saying.

Any help would be greatly appreciated!

Thanks