In my opinion it is pretty close to truth the statement you wrote in your question. Not entirely truth as the woman is already married to that guy, but the attitude is still of a prostitute. Prostitutes usually accept to have sex with different men for money, otherwise they wouldn't do that with so many and especially with anyone so we can say that they offer their "body and sexual" abilities for something in exchange which is money in general. Now the woman you mentioned about usually has sex with her husband as they are married, but in order to get something from him she might "offer some extra", she will trade some of her for a favor. It's probably that she was not in the mood for sex, but still did it because of that favor.