If the girls want to give it a try they will almost certainly appreciate it. Everyone who has tried a bidet that I personally know has preferred it to just TP. Plus, I believe (from experience) that a bidet is essential if you're a mensurating girl or woman who uses sanitary pads.

But the best thing about a bidet attachment is one or more toilet users can choose to not use it and it's not any different from a bidet-less toilet. It doesn't get in the way or anything, so it's there if you want it but not any inconvenience if you don't. My husband didn't use ours for the first year we owned it but after he eventually gave it a try he's now a regular user.

Plus it's so ridiculously cheap ($40) that it's worth trying out.

It takes them a bit more getting used to be they benefit more, too. Make sure to get a model that can adjust the jet angle sufficiently.