Cold sore


So my mom has what looks like a cold sore just above he lip it almost looks like it under her nose... she comes over to play with my son who’s 12 months every day.. she said if she ever had a cold sore she wouldn’t come over.. should I ask her to stay home? Is it even possible to get a cold sore under ur nose? Is my son old enough now that I don’t have to worry about him get it. (That he’s past the age where it’s deadly)