If she missed her period I would suggest to test.
But I know, that switching pills back and fourth isn't good and could possibly mess up her cycle and that's why she could have missed her period.
Did she get her last months period on loestrin correctly? Just curious, because you said she's been on that bc for 2 months now so if she got it last month I don't see why she didn't get it this month.
What about any other symptoms?
You will only know for sure if you have her take a test, I would suggest a digital one, the ones that say pregnant or not pregnant.
Good luck.
Liveinlove