I agree it would be nice if Google/Android were to lock down its app icons because they're too easy to accidentally move/remove! Ugh, so annoying! While Apple iOS also doesn't lock down their app icons, it's actually harder to accidentally move/remove app icons than on Android.
Sorry this doesn't exactly answer your question because it doesn't involve an add-on app to preexisting launcher but, there's a very thoughtfully designed, lightweight launcher called Smart Launcher that has an important feature called "Prevent Modifications," which solves the problem of accidental moving/deletion of app icons you and most people are having.
I bet your mother would enjoy this launcher because my mother who's not good with tech finds it easy to use (this was after she complained about Samsung's Touchwiz interface).
Other unique benefits/features of this launcher:
(1) Conserves screen real estate by allowing two actions per icon/app--secondary action done by double-pressing an icon/app; allowed actions include app, folder, widget, shortcut, etc.
(2) Arranges home screen apps into a circular (other choices as well) pattern, making it easy for user to remember where things are, so access is faster.
(3) Instead of showing apps collection page by page, it groups apps by their categories, modifiable by user. It's like the Linux Mint Operating System's start or app menu.
(4) Rarely used apps can be hidden by user.
(5) Since it's among the most lightweight of all launchers, it conserves battery and valuable resources which could be used for something else, which is crucial for slower, older phones.
(6) Advertised to work with "OK Google" voice command, though I've never tried it because I don't need it. Uses a Contacts-searchable bar on the homescreen.
(7) Doesn't require rooting.
(8) I've been happily using the Free version which meets my needs, but if you find you like the additional features then they're in the Pro version.