Unless her skin is really bad, I'd probably skip foundation for now, honestly. Most people I know skip it in the summer if at all possible, and it's not always absolutely necessary. Concealer, however, is a must. I'd say the select moisturecover from MAC. It can be tricky to match, though, depending on where she'd want to use it. I, for example, am generally lighter than NW15 and need an NW20 to cover my bloody undereye circles.
Based on an NW15ish skintone, my recommendations are as follows:
I'd say... concealer, a self-made quad with a good highlight (I LOVE blanc type since it's matte, but Phloof! is great too. Shroom does NOTHING for me), two neutrals (Sable and All That Glitters go wonderfully together, and the hint of plum in sable would go nicely with her hazel eyes) and one fun colour (if she likes purple, it would go nicely with Sable - satellite dreams, perhaps?), one blush (I love peachtwist or shy beauty BPB), a brush set (honestly, the quality is just fine for someone first starting). Also, some sort of base. My favourite is bare canvas paint, but bare study paint pot could also be used as a shadow in and of itself.
I'd go drugstore for mascara and lipgloss. They work just peachy, and at a much lower cost, which saves you and shows her that makeup doesn't have to all be higher end to work well. I know some people would disagree, but I'm a maybelline mascara girl (my lashes are super long and nicely full on their own, and I love how intensely black their mascaras can be) and Rimmel vinyl lip lipgloss or the vinyl stars lipgloss works great. The Kiss Off stuff is to be avoided, as it smells and tastes fairly awful. This is also where I would get eye makeup remover. Plus, I'd grab at least a black and a brown eyeliner pencils (again, Rimmel is great for this. I have a whole slew of Rimmel pencils mixed in with my MAC). I use baby shampoo to clean my brushes, as I find it does a wonderful job of thoroughly cleaning them, and is gentle and conditioning enough to keep them super soft; I have a Quo brand blush brush that actually got softer after I washed it a few times with baby shampoo.
I don't know if she's the type to go for lipstick. I know many younger girls don't ever use it, and there are certainly decent drug store ones she can pick up later on her own.
In summary, I recommend:
-select moisturecover concealer
-an empty quad
-blanc type or phoof! pro pan
-sable pro pan
-all that glitters pro pan
-satellite dreams pro pan
-peachtwist blush or shy beauty powder blush if you can still get it
-mac brush set
-neutral paint or paint pot
-drugstore mascara
-Rimmel vinyl lip or vinyl stars lip gloss or two or however many you think
-Rimmel eyeliner pencils in black and brown
-drug store eyemakeup remover
-baby shampoo
I think that is everything one really needs to get started. Foundation is a very personal thing that if she wants, I'd say she should look into getting herself - plus, she can always ask you for help. It won't totally break the bank for you, and I believe it's important to remember that there is some great drug store makeup that holds up right next to the more expensive stuff. The only other thing I'd possibly add on to that list would be a pressed blot powder.
Cheers!