Hello. Welcome to Healthcare Magic. I can understand your concerns about an unwanted pregnancy: even if you didn't insert your penis in your girlfriend's vagina, if any of your semen came in contact with her labia there's a chance she could get pregnant. If taken within 24 hours, an i-pill is 95% effective for preventing pregnancy in situations like this.
Most side effects of i-pills are relatively mild: nausea, vomiting, diarrhea, tiredness, breast tenderness, headache, and dizziness are common. Many women who take the i-pill also experience a change in their periods: early or late periods are common, and some women spot throughout their next cycle after taking i-pill.
One possible serious side effect of i-pill is an ectopic (tubal) pregnancy. If a pregnancy does occur after taking i-pill, it's more likely to be a tubal pregnancy. Therefore, if your girlfriend develops severe lower abdominal pain during the six weeks after she takes i-pill, she should see a doctor immediately.
I hope that answers your question, and good luck!

Hi Thanks for posting query on health care magic.

I pill used for emergency contraception doesn’t have much side effects, however ,as every medicine has side effect it too has side effects and its side effects are divided into two types:

Shorter side effects may lasts for days

Nausea and vomiting; occur in 10% of women and last for 1 to 2 days
Abdominal cramping. lasts for few days, if persists for more days, consult doctor
Breast tenderness
Headache
Feeling tired

Longer side effects

Spotting and bleeding:. spotting is light bleeding that may be red,brown,or very dark .This may lasts until the next period which should come on time, a week early or a week later than you expected,
If the bleeding is too heavy or associated with other symptoms,consultation with Doctor should be sought.
Presence or absence of side effect doesn’t tell you whether medicine has worked or not.
There are on other way to prevent pregnancy after unprotected intercourse, other than emergency contraceptive pill.
However if emergency contra captive pill fails (pregnancy test come positive),the other way is to go for Abortificient pill.

Hope I answered your question.