From above sexual activity and precum through underwear, chance of her pregnancy
is quite rare.
Pregnancy depends on proper timing of unprotected sex with ejaculation inside vagina and ovulation (14 days prior to due date) or fertile days.
Here, she must wait for next coming period and undergo one home pregnancy test if it is delayed more than 1 wk to clear doubts.
Hope, it helps for you. Good luck and practice safe sex