Worried boyfriend, precum, birth control, plan b pregnancy risk

So yesterday, the girlfriend and i were messing around. She had on her thong, while i had on nothing. She was straddling me and grinding, but my penis was pressed flat between us with the head pointing up towards me. I had her climb off from on top of me, and when she did, i felt some precum. I didny think much of it then, until i got home about 30 minuets later. She got in the shower as i was leaving, and had been/is regularly taking her bith control. I told her about it, and we got spooked, so she went and got the Plan B pill and took it. The incident happened around 12 noon, and she had taken the plan b pill by 3:40 pm same day. She says were fine, and that she goes for a check up on the 15th and that she will know for certain then. Shes trying to put me at ease, but i just cant shake the fear and panic. Is there any remote possibility that she could get pregnant from this? There was no penetration at all, and as far as i know no precum entered the inside of the vagina. She says she never felt the pre cum at all. Am i worrying myself for nothing?