The first time I took a quilting class, I was so nervous, I never thoughrt I'd get there, let alone stay long enough to get thru the class! I sweated buckets thru the whole thing, wondered why everyone else was so fast, got things done, and still managed to laugh and enjoy each other. Of course, not all of them were newbies so, looking back I realize I was trying to keep up with some very experienced quilters.
Now-a-days, I've put that behind me and enjoy the experience. But, I remember wha it felt likek and make an effort to help newbies, really anyone, within arm's reach at a class. Give it time. You'll get there!! I wasn't home schooled but lead a very sheltered life and it took time, experience, and the help of others to conquer my fears. Try to relax and enjoy the time with your MIL. If anything, she already knows you'll be nervous and will be anxious to try and make you relax.
So, the two of you should relax, huh?!! Try to have fun.