Ok back!
First thing:
The letters that were found at Wendy's were correspondences between herself and another person. The letters were not from Brittney. There are several of these letters.
I have taken screen grabs of the letters images in case anyone wants to analyze them, however I think I have a good conclusion here:
There are no margins, the lines are blue and there is no perforation: this was written on a white legal sized paper.
Who has this sort of paper? Inmates.
This was written in pencil: inmates aren't given pens.
This was written in pretty feminine style but not cursive: Anyone 30 and over normally writes in cursive/normal. Cursive is no longer taught in school and hasn't been for awhile. This is person is feminine and under 30.
They spelled a lot : alot. That's the only thing I noted as being wrong.
They listed Jennifer first - this shows importance to the writer. The writer lists people and if you know anything about analyzation when it comes to lists: people always list who is more vital to them from most to least.
The list goes:
Jennifer
Brittney
Wendy
Mendy
Odd that she didn't start out saying "You". This person must know Jenn personally.