I was raised Lutheran and am Catholic now.
To make your mom comfortable, you could jot down a little “program” for when to sit/stand/kneel in your parish, and remind her that when we say the “Our Father” we pause after we say “deliver us from evil.” Also, remind her that she should not take communion in the Catholic church.
I think those are the big differences that a Lutheran needs to know to feel comfortable in mass. I can’t tell you how many times I found myself blushing because I stood/knelt/sat at the wrong time or said “for thine–” when everyone else waited for the priest to talk. (And later, when I found out that I was wrong to take confession, I felt bad for unknowingly dishonoring that particular Catholic belief.)