3R - Firstly I have never heard of this method being used so early on in a pregnancy, but then I am not a doc! (That's right, I abbreviated it) ;o)
I have heard that false negatives on pregnancy tests are very common and you can have a number of them but a false positive is almost impossible!
Secondly - I know what this girl is like from past experiences and she could lie her way out of any situation! It's got a lot to do with 3R as her partner is one of the main carers for his little brother who is the one dating the girl who is lying.
Thirdly - 3R ignore the idiots on here who pick holes for the sake of having something to say! They clearly couldn't put any decent imput into your Q but wanted to be involved in some way or another so decided to go the route of being rude! I have headr PG be used as pregnant before and I have even seen it on this site before so don't worry about it. And even if it hadn't ever been seen before.... It's not that difficult to work out and it's no worse than this lot using Lol, Lmao, Pmsl, Wtf etc!!!!
Love ya Xx