Only thing to do is a DNA test
She needs to be sure she actually was in the right time frame to be ovulating when she had the eventful week with the guys.
If she wants, she can send in her info to the DNA/Paternity community here on MedHelp, and we'll help her figure out if she really was ovulating at that time. Like this:
First day of previous period before getting pregnant:___________________
Date(s) of sex with guy A:______________________
Date(s) of sex with guy B:______________________
Cycles are:
[ ] regular ___ (days from day 1 of period to day 1 of next period)
[ ] irregular
Have had an ultrasound [ ] yes [ ] no
Estimated due date based on ultrasound: ____________
(or)
Estimated due date based on calendar or app: ____________