Hello & welcome!
If you don't feel comfortable with her using that high a lift, *tell* her and ask her to use a weaker form. But she might be right, and your hair might not lift well enough, leaving you with brassy roots (and I'm sure that's not what you want).
If you are dark brown (the way your roots grow in), you need a higher lift. That's true.
Maybe have a consultation with someone else and ask them what they would use. That's the only way about this.
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