I took a blue dye test that looked just like that and the directions said if the line was really thin then it was a negative. Definitely take a pink dye!
I'd worry about it being an evap since its not a thick line. How long after she peed on it was this taken? Most of these will show a thin line after a while.
i took a blue dye test that came up even lighter than that, and that pregnancy resulted in a baby boy who is now 9 months old.
I've also had a pos like that on same brand if test and results were like that, he's now 8 years old. So hard I guess to tell the difference between evaps and crap positives on these :/