S.E.
Yes...you can get herpes simplex 1 (cold sores) in the genital area...It is not the same thing as herpes simplex 2 which is genital herpes...but still very nasty and painful, though not as serious.
It is HIGHLY UNLIKELY your MIL passed this on without "direct contact" to your daughters genitals, so I would just stop obsessing. I know you are worried, believe me I understand...but there is nothing you can do about it. Life goes on, and honestly...there are way worse things in life than a cold sore. We aren't talking leprosy or AIDS, so just calm down, and on the off chance she does show symptoms...deal with it. It isn't life threatening and debilitating, on top of the fact that no amount of research or worry is going to change it. From here on out demand your MIL be more cautious...and leave it alone.