This sounds like a normal adjustment that some women go through when they stop hormonal birth control.

when i canme of it i too experianced things like this, however if she is really worried get a test from the pharmacyno one needs to know, but it would show on the test, lateness is a sign yes but it can be also changes as her body does change back into a normal rutine, but if she wants to make very sure id advise a test from the pharmacy there are some really good ones and cheep, too, but also i have been told that women's periods are not always regular,and i was advised that after talking the pill it could be a while before i got back into a normal rutine, i hope this helps a little