Ah, so you're saying she can apply anytime from around the 10th of May (that's 28 days before she's 2 years here) till her visa runs out on 16th August?
YES!
But just make sure UKVI will get her application before 16th August or else, it will be classified as late application and will be refused.
-=rayna.keith=- ...When you realize you want to spend the rest of your life with somebody, you want the rest of your life to start as soon as possible...