Girlfriend and I had sex, condom broke, she took plan b, when should she have her period?

If she has normal periods she won't ovulate a week before her period usual ly we ovulate two weeks before and two weeks after our periods the safe zone but sperm will live in the cervix for 3 days... Hope that helps

You have done all you can do at this point. No contraceptive is going to be 100% effective and condoms alone are one of the lowest effective ones there are for this reason, they can tear and break. For best protection when using condoms, you should also use spermicide because it helps kill sperm in the event of a tear or break. The most effective forms are the hormonal birth control methods including birth control pills (oral contraceptives), Depo-Provera injections, Implanon/Nexplanon implants, Nuva Ring, or the IUDs like Paragard and Mirena. These are all about 99% effective when used correctly and consistently. Plan b is only about 80% effective. If you are going to be mature enough to engage in sexual activity, you must be aware that no contraceptive is 100% so there is always the slight chance for making a baby no matter what you use and as so, you must be ready to deal with those consequences. Sex is not a game for fun.

There is no way to tell you that. It's 80%effectivs. Her period will probably be late. It usually is after plan b.