The green Always ones are ever-popular. Dark green are the ones with wings and light green are the ones without.
However I always found "Cottons" to be more comfortable. They are also pre-wrapped and disposable, they are just as soft and absorbant as Always (ie not like the own brand ones) but they have fewer chemicals in and are slightly less "sweaty", especially in black school trousers! They're the same price as Always and you can get them from Boots. (I don't really buy the biodegradable thing, but the other points on them are excellent)
I used these right up until I discovered mooncups and they are the only disposable pad I'll use if I get caught out now.
You could get her some pantyliners as well? I always found pantyliners much of a muchness, tesco own brand ones are just fine. (Though Cottons make pantyliners too.) You can get individually wrapped ones of those too. They're handy for discharge and for getting the hang of wearing something before periods start so that pads don't seem so daunting.
Definitely agree with an emergency pack - small make up bag containing a spare pair of knickers, paracetamol, couple of pads, and a nappy bag or one of the clear veg bags from the supermarket in case of knicker accidents or lack of sanitary bin.