Question about female shoe sizes and hand bags?

Hi my girlfriend's birthday is in 2 weeks and I wanted to buy her a pair of Jimmy Choo shoes. I didn't know her exact shoe size so I decided to check her sneakers. I was wondering if sneaker sizes are the same as high heel shoe sizes? I am also thinking of getting her a designer hand bag but never bought one before. Aside from looks are there any specific sizes or hand bag lengths I should be looking for? thank you!