I gotta know if this is normal, because it seems strange to me. My cousin has been cloth diapering her girls for years, but I don't agree with how she does it. She uses prefolds and flats, but sews washcloths into the diapers so she can "change them less often". The girls constantly have wet, red bums from all that moisture. I'm a firm believer that if the diaper is wet/soiled, change it!
My aim was for a diaper to not leak but that was for one wetting episode.
I do know many that use disposable that try to leave it on till it won't hold any more
I don't like that approach either. At this point (DD is 28 months) we mostly use pocket diapers which have that stay-dry-ish layer but I still try to change her every time she pees. I check frequently and change her whenever her diaper is wet. Letting her sit in a wet diaper (or dirty, of course too! but I think most people do that) seems like not only inviting a bum rash but also counter productive to potty learning - I worry she would get used to having a wet bum and then it wouldn't motivate her to pee on the potty eventually. Mind you we do still go through a lot of diapers daily (we probably average around 8-9/day) but that doesn't bother me, they're reusable and I'm glad that I can change her as often as I want without worrying about the cost.
For night/naps I could see adding extra absorbency though, I always did additional inserts or diapers with more absorbency. At this point we actually use a disposable overnight and I take it off as soon as we get up in the morning no matter how much/little pee it has in it.
Perhaps you could suggest to her re: the red bums that she could get some inexpensive fleece to cut up into liners so that it helps pull the wetness away from their skin? It doesn't really sound like she'd be too receptive to advice about changing them more often...