well i think you've got to do one or the other - either is OK with me - but of course I'm not the one pining away for her.
If you think there is a chance in hell that she is interested in you - just tell her now before she gets too involved with BF#2. they can't be that involved yet -... and how many guys helped her through the breakup anyways??

If you think there really is no chance in hell that things will work - then just move on.

The in between status will give you an ulcer!
The whole timing thing IMHO is a myth - if love is meant to be it will be - and you aren't going to ruin things by your timing of telling her.