After all the understandable moralizing and pointed disgust, Tgg, let's get down to some unadorned, basic tactical advice.
Only you know whether or not you want to meet this woman.
If you do, let me just say that a through the pants handjob in the uncrowded theatre of a movie matinee can be a particularly pleasurable experience -- very, very erotic because of the danger and necessary limits.
Want a little more? How about a front seat bj at the far, untrafficked end of the movie theatre parking lot?
Trust me, you probably do not want to see this woman entirely naked. Not to mention, the logistical problems (angle of entry, fat impeding penetration) of coitus with her own large, large self.
But, if you are not psychologically prepared to be in control of this situation, and/or you can't shake that bad, bad feeling about what might happen, just don't do it.
Lastly, if you go for it, be honest and upfront with this woman about what you want and don't want. She is a fellow human being and a child of God, just like yourself. Step below this absolute minumum level of ethics, and you will have to answer to your own conscience ever after, God or no God.
So go, negotiate, be honest, ask for what you want, set the parameters which you would be comfortable with, or get the hell out of this, OK?