Turns out she is the same lady that my manager advised against letting her lease again.  

But, from my experience, you could end up with them taking over the living room watching TV that you're not into.If you share a bathroom, get a weekly cleaning lady and include that cost in the rent.  

My worry is that the girl might split at any moment. together they make a lot over the 2.5 time the rent.Applicant #2 Older lady in her early 40s no kids no husband. works as a nanny full time ($2800) and work part time as care giver to elderly ($975) and her score is 675. she seems like a better choice.I would really really really appreciate any input!

My assignment for you is go back to that lady and increase her rent $30.

Of course if they were not willing to then work with me that would be another story but it seems like this lady in your situation is trying really hard to keep her home, but in the end it is entirely your call and your budget and what it can sustain. 

I didn't jump on it and she moved to a cheaper a bit more run down area.Now, I had a bunch of people flake and my advertised rate is LOWER than what I could have had this lady just stay another year for.

To the lady's benefit, she may have misunderstood your question.

On a side note, something funny happened, I'm ready to offer this couple the house but got an email 2 days ago from single professional lady and she mentioned if she likes the house she's ready to offer the entire year's rent up front!

I can however say that the scenario you outline is not a wholesome one - agreeing to one rate and then paying some kind of supplement on the side.

My first property was a live in duplex, and now four years later the lady who lived next door is still there.