Peter's mother-in-law

In Credo Gathering on Tuesday we had a look at the story of Jesus healing Simon-Peter's mother-in-law, and I've just been having another look at it:

Now as soon as they had come out of the synagogue, they entered the house of Simon and Andrew, with James and John. But Simon’s wife’s mother lay sick with a fever, and they told Him about her at once. So He came and took her by the hand and lifted her up, and immediately the fever left her. And she served them.
(Mark 1:29-31)

Sounds a bit like the lads have had a big day casting out demons, they're getting a bit hungry and tired, so they turn up at Peter's mother-in-law's, hoping for a feed. But it turns out Peter's mother-in-law is sick in bed. I think if I didn't already know the story I'd expect the lads to be looking after her and asking if there was anything she needed, but instead Jesus heals her, and she gets up to serve them.
Another thing I was wondering about was why Peter didn't know that his mother-in-law was so sick. And was thinking that if this passage was interpreted as a mother-in-law joke, then Peter is probably responsible for his mother-in-law being so unwell.