We were just having this discussion
on this other thread.
As her five years will end 13 November 2021, and she can apply for ILR up to 28 days before that, she'll want her 30-months FLR(M) to get her to 16 October 2021 at the very least.
I believe she can apply for FLR(M) up to 28 days before her 30 months in the UK, which is 19 March, 2016. However, if she applies that early and gets a super-quick decision, she will be cutting it fine for getting ILR eligibility before her FLR(M) expires.
Having said that, if she's able to apply before fees (typically) go up in the first week of April, she could save quite a lot of money.
The P60 is optional. I would base my decision on timing for ILR eligibility and cost of the application.