If she had sex with a dude after 6 months and ended up breaking up with him, then maybe she just wants this time to be a sure thing. Girls generally think of dudes as more physical than emotional so she might be testing you. (Girls are bitches like that. =D)
If you're serious about her, then take her seriously and wait it out. If not, then just go with whatever you feel. Most girls like to over-analyze things so if you've got something to say, say it straight, no mixed messages.