This is well-written. I don't really know much about the people you've based it on, but you make some great observations that add real depth to your characters. For example:
"She hadn't even been gone a year, but it felt like an entire lifetime had passed."
And:
"I wasn't paying attention to the time as I should have been. Mostly, though, I wasn't paying attention to the fact that what I was doing was as wrong as wrong can be."
Some lines are a little obvious though, and that can undermine your flow. For instance:
"Lucy went into a depression."
Although you've got heartfelt recollections on either side of this, I think you could have described this event more subtly- perhaps by alluding to the symptoms of her depression. That would also be more personal.
Overall, however, I think this is nicely structured and composed.
OMGee this story made me cry :'( i loved it and i feel so bad for frank. its wasnt your fault frank you should know that *sobs* youre an amazing writer you know