i have an 18-55 and use it regularly and am just starting to build my glass. It sounds like for what she wants, a tele lens is your best bet. What you want to spend defines what you'll get
Everyone is right, the 70-200 f4 non IS is the best bet, It's got wicked optical quality, and usually you can get one for around 500 used, 600-650 new. This is also a great lens because if she wants to shoot macro with it, it's super sharp all around and especially at the edges, which is a necessity in shooting macro
You could go for a 70-300 as well, and while it's got a greater focal range than the one above, it's much softer, especially past 200 so it wouldn't really work for macro as well, and it just won't perform as well
Depending on how much you want to spend and how into photography she is, that'll determine your decision