Kind of confusing when you say disappears. Never heard of them disappearing when activated. You mean when the programs icon is closed, it's a small icon like this...
Then when you open the program from the taskbar icon, it morphs into this..
Another example, using a custom Firefox icon, which will change into the original FF icon when activated..
If that's what you mean, that's normal behavior for having Never Combine. I don't think there's a way of changing that, not even sure how you want it to be changed. If she doesn't like it, have her use Always combine, Hide Labels. The icon will basically stay the same closed or open.