Abc

Of course you both realise that plan B is not for frequent use as a form of regular birth control but for those emergany and when there is a chance that other forms may have failed. So please have her and you look into regular birth control methods used for regular use of there is going to be on-going sexual relations.

And of course she is to take the 2nd pill within the proper time frame also.

But yes, it can effect her period.

If taken very soon after your period has ended plan B can actually make your period late by a week or so. If taken when your about to experience your period it can have the same effect. If taken later in the cycle it can actually cause an earlier period. I took it a few months ago and did extensive research afterwards. The hormone dosage really mucks with your system for about a month. Your girlfriend my experience a later period as a result.