The sooner the emergency contraception is used, the better the chances. 24 hours later is a fairly long wait time. And if she missed the Pill for two days, that's certainly plenty long enough that she could have ovulated, especially as low as the dosages are now on the Pill.

This is why you should always use a condom. Wear one from now on no matter what. As far as this situation is concerned, I'm sure you are worried. How long has it been since y'all had the unprotected sex? If it's been longer than a couple of weeks, sure, go ahead and get a pregnancy test and see what the results are. It may be that having missed two days of the Pill and then having used the morning-after contraception, which is a higher dose of what's in the Pill, it's just thrown her cycle off. Let's hope so!