Ash will not cut warmth when you bleach someone's hair. All hair when bleached or lightened up many levels pulls warm. To cut the higher levels lets say 8 & up you need to use Pearl tones or if your using Goldwell a little 10V will help cut some of the warmth.

What was the brunette color? A level 4? If so you are only going to be able to safely lift to lets say a light orange or dark gold stage, from there you can tone it to get an acceptable color to wear for several weeks. The Light Orange in the underlying pigment that is being exposed by bleaching the color out of your hair. In the meantime deep condition your hair weekly or every 3-4 days with a deep conditioner and use a moisturizing shampoo to help get that moisture and elasticity back into the hair strand that was just chemically dried out by the bleach.

You can try rebleaching it in several weeks to go even lighter but for now my best advice is give your hair some TLC and rest for several weeks. Continued bleaching without caring properly for your hair can actually caused breakage at or near the scalp of your hair or if the bleach is too strong it will melt the hair right off your head. I've seen this happen to people don't let it happen to you....do it the right way like I've explained above.

G'luck