Yeah... but... it wouldn't happen.
Marine Snipers are a very select group. They take something like a hundred candidates, and of that hundred, they actually make only ten of them marine snipers (and ten spotters, one for each sniper). The rangers are a pretty select group, but not as exclusive as the marine sniper. But to do both would mean that A) She was an army ranger (I'm not sure women can become Rangers), and THEN she would have to join the marine corps, and qualify to become a marine sniper, and then be picked for the training, and excel at it. Then, after her dual-corp training, she would go overseas and train with the SAS.
I only mentioned three of her groups of training. There was like 15 on the card. I find it highly unlikely.
-kv