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Emergency contraceptive pills are effective only if taken within 72 hours and later than that chances of pregnancy are possible.The pregnancy test being positive indicates that conception has occured and also symptoms as missed periods and cramps in the abdomen are also indicative of that.
She needs a urgent referral to a Gynaecologist for confirmation of pregnancy by Blood test and USG scan so that further action can be decided.
In Early pregnancy upto 8 weeks, Abortion or MTP can be done medically by using oral tablets but they are available by means of prescription only and for a woman under 18 consent by a guardian is required for this.
Kindly ask her to talk to some family member and visit a Gynaecologist urgently.Do not go for other self methods as they would do more harm than better.
Take care!