hot roots

My hairdresser gave me hot roots.... I said wasn't happy but she doesn't want to bleach because i am pregnant Do you think I could even this out with a red (Majirel 6.66 at 20 vol) on the ends up to where the hot roots start and chuck it on the roots area for the last ten mins or so?

So I’ve been using matrix socolor an color sync for 5 years...but recently I’ve been getting hot roots! I use 20 vol with so color an for grey coverage,what am I doing wrong?? I’ve tried going a shade darker but don’t want to go to dark heeeeeeeelp please an thank you