650 tyres - Where can I buy?

Gatorskins are shite for grip. Try some GP3000s or 4000s instead.

I actually ride Michelin Pro Race 3/4s year-round on all my bikes including 650c. Very dependable and stable in the wet, and pretty durable for me (53kg, inflate to 90-100psi). They aren't cheap though, and I check them before every ride for bedded stuff and pick it out. Which is a bit high-maintenance for many riders, hmmv.

Ah yes - sent her a link to the 4000S. I have the 700c x 25c 4000S on my road bike and they seem to stick to the road pretty well.

Her bike is rather small - I believe it's a 49cm frame. With regards to weight, whilst she is fairly light, she often has a pannier full of stuff, plus mudguards etc.