how to make purse strap adjustable?

i bought a cross body purse and i really like it, but the strap is too long. the purse sits below my hip, but i'd rather have it on my hip. the straps are not adjustable, so my mom offered to modify it for me. she bought D rings and plans to take the strap off, add the rings, and sew it back on. it's a fake leather sort of material btw. but she's not really sure exactly what she should do and wants to know exactly what to do before she does it.

so is it possible to make an adjustable strap with D rings? or do we need something else? i don't want to tie the strap or do that thing where you fold the strap and tie it with a scarf, i think that looks dumb.