I think her age is difficult to determine. I would have guessed around 18 years old, but could easily be slightly younger or a few years older.
Doesn’t look much like a badge on her beret does it Roobarb? No lettering or identifiable emblem. Not even sure a school uniform would have something like that on a beret would it? Maybe the cross shape is significant, though that could be decorative pearls or stones as it looks quite brooch like I think.
On the original photo is there anything where the pale spots on the lapels are?