I was on OrthoTriCyclin and the "Lo" version for about 8 years. I went off the pill in April 2 years ago. Got my first period at the end of July, and never got a second period because I got pregnant in September.
My sister had been on TriCyclin for about the same amount of time and got her period back like clockwork the next month. So who knows? Does she exercise a lot? Is she underweight? I think my competing in triathlons that summer and being a bit underweight probably contributed to it taking longer for my body to kick back into gear. That, and my periods were frequently irregular before I went on the pill.
She can tell whether she's ovulated if she starts charting her temperatures - we started doing this after about a month because I kept wondering when oh when could I get pregnant.
I guess my point is that everyone's different. If she's not ready to be pregnant yet she needs to take some steps to avoid pregnancy until she is ready - either condoms or at least keeping track of her fertility (see the book Taking Charge of Your Fertility - this is a *great* resource for both avoiding pregnancy and trying to conceive).