Safe to use same litterbox now?

So after about a month and a half after introducing the new kitten, they are starting to use only one litterbox. I didn't expect this at all as my older cat is slightly territorial. But after looking in the litterbox that used to be hers (the older cat, Hollie), there is no poop! Which means that she has been going in the kitten's box (I thought there was alot of poop in there for a kitten ). So if I completely take one box away is everything going to go OK? I don't want to find poop somewhere random, but I would really like only one litterbox in my small bathroom. Thanks!

It is highly recommended that you have one litterbox per cat plus one. If you really have no room then I would keep two. Many cats don't pee and poop in the same place, so you might have problems taking one away. My four have six boxes and it is strange that while some cats pee in one box and poop in another, others do the opposite but in the same boxes, if you see what I mean.