Dearest starliteny1,
Thank you for being so brave so as to ask such a question, even after coming so close to a disaster.
We, as hairstylists, always seem to offer instant results, with low prices, to clients that do not entirely respect us.
The correct procedure is to totally strip the old ( fantom ) color, with a product like "RUSK'S" Elmin8 or comparable.
Then refoil Highlites and lowlites to achive desired grey blending.
Discussing the full process , time and price should be included... before you start.
But most would start, get their client trapped and applogise, to try and be able to finish the desired result.
I'd be more than happy to help out in any way.