I was seduced by an older woman, what do I do?

I was watching my good friend's baseball game, and I sitting next to his mom. We started talking with eachother, telling ourselves about eachother, and next thing I know, she grabs my hand and places it on her bare upper leg. She held it there for about 5 seconds and I got up and excused myself to go to the restroom. I'm 19 and she is 46. She really isn't a bad looker for her age, but now I'm trying to figure out how to approach her next time I see her at the next game. If she's trying to get into my pants, should I let her? Should I allow myself to fall into a relationship with this woman? But on the other hand, I know it would cause a lot of tension with my friend. What should I do?