"Say What You Feel"

This was the conversation I had with my Mother-In-Law (visiting from PA) yesterday;
"We're going out for pizza for lunch, you want to come?"
"Oh, that sounds like fun.  Is everyone going?"
"Yes, me and all the kids...you wanna come with us?"
"Oh, no, I don't want to be a bother..."
"You won't be a bother, we'd love to have you."
"Well my knee still hurts from the fall."
"Okay, I'm leaving in 20 mins...I hope you come."

Ten minutes later after talking to my husband who said, "what is she going to do...sit home?":
M-I-L was still on the couch...
"You should come with us to lunch....it will be fun."
"Oh, I don't want to be trouble to anyone."
"You aren't trouble, we're eating lunch."
"Well, I don't think I'm going to go."
"Okay..."

Five minutes later I go to grab my keys and see she is standing by the door dressed and her purse is over her shoulder.  I was shocked, "Oh, you're coming!  Great, let's go!"

Why don't people just tell you what they really feel and think?  I don't like to guess and I don't like to beg.  Just be real and be honest. No one gets hurt and everyone lives a healthy, truthful life.