Is the test line as dark or darker than the control line? It is normal to see two lines on an OPK but if the test line is not as dark as the control line, it isn't positive.

If it is as dark or darker than the control line, is it getting darker every day - it may just be leading up to ovulation. It is not that uncommon to have a few positive OPKs leading up to ovulation.

Is she temping and charting? The best way to tell if she ovulated is the rise in her temperature.

If her OPKs continue to be positive and she isn't on any sort of medication that could be contributing to that, it may be worthwhile for her to take a HPT because continuing postive OPKs can also indicate pregnancy.

If you want more info on OPKs (and HPTs) - this is a great website with lots of info. The lady that does it does heaps of experiments with all sorts of OPKs and HPTs and answers questions I would never have even thought of. There are also photographs which I think is great because sometimes it is hard to imagine what they are referring to without visuals ... PeeOnAStick.com