About pregnancy. Of her being pregnant?

I had unprotected sex with my gf on 17th April and i gave her unwanted 72 pill within 23 hours on 18th April.. Her Cycle Started on 12th April and ended on 16th April.. And then on 17th we had unprotected sex.. She started bleeding on 22nd April that is the 5 day after taking Emergency contraceptive pill.. Her bleeding Ended on 27th April.. She Vomitted 1st time on 2nd May and then again on 5th May.. Now today Morning.. 21st May.. She also checked her pregnancy with home pregnancy kit(prega news).. And it showed Negative result.. The thing to worry is that she is not getting her monthly cycle and she is worried about it as its already late from her regular schedule time.. When she can expect her Periods again? Even after having Negative result in home pregnancy kit.. Is there still any chance of her being pregnant? Kindly Reply.. And Help us.. Thank you