Thanks Lizzy my dear! lol
Well, being you already have the colors & the peroxide, you pretty much have what you need. Make sure you have gloves, a timer, combs (one tail comb & one large tooth), some old clothes to wear, and also you will either need a color application bottle or a cup & brush. Now, you said that you're using two colors, so I'm not sure what % of each color her stylist uses... you'll have to ask. It might be 1:1 it might be 2:1 or whatever... so I really couldn't tell you being I don't know her hair or what she has done. You'll also need to know how long her hair takes to develop... and process time varies depending on the peroxide volume & the structure of her hair. Usually on hair that is already color treated - with no grey- I'd give it about 15-20 min. then keep checking every 5 min. thereafter. First apply to roots, and work down the shaft, & when she is about 5 min. away from being done, comb hair from roots to ends to distribute the color, and then let sit for the remainder of the time... rinse, shampoo if you'd like (I do) and condition. Always try to wipe color off skin if you see it, and coat the perimeter of the hairline with conditioner or vaseline... (only on the skin) Color removes color, so if you're rinsing her out and see some color on her skin - rub the hair (with the color in it) over the spot on her skin. It helps a lot.
I'd talk to her stylist and get as much info as you can on how her color is mixed, and her process time, as well as if she needs heat or no heat. Sorry if I confused you, and couldn't help you more - but not seeing her hair or coloring it before... it's kind of hard to give a general answer...
