500k cap gains exclusion for (about to be) married couple

[Lem Diaz]

I'm getting married Jan 28th 2017. My Fiancee has been living with me for just over two years, but still did her taxes and had official mail delivered to her old residence (her mom's place). We will plan on filing jointly for 2017 taxes. I am the sole owner on title and the mortgage. 

My question is whether or not we'd qualify for the 500k cap gains exclusion for married couples after Jan 28th? 

I think yes, but I'm worried about the part where I have to prove that she lived there for the last two years since her taxes were done with a different street address on them.  What constitutes proof in the eyes of the IRS?