How to separate mistakenly joined people tags

I have imported about 10,000 pictures and tagged many of the people. When I opened up my Photoshop Elements 15 today I find that it modified my work as follows: Whereas I had about 600 tags of Person A and about 600 tags of Person B I now find I have 1200 tags of Person A. Person B is still in my list of categories, but now has very few tags.

So now I need to separate these 1000 tags back into two groups of 500.

I could look at the 1,000 face images and use the "not this person" option - then re-tag them as they would show up in the un-named group.

Is there a better way?  The two people look somewhat alike, especially when they are very young.  If I delete both people from my list of tags, would the program attempt to group them again, or would it show all of them as single faces to go through.

This is frustrating because when I pulled pictures in originally, I did so in groups of pictures which were dated, so I had context in which to help the facial recognition system differentiate the people. Now I do not have that context, making a big job even bigger.

Also I probable have about 5,000 photos to add. My computer has plenty of capacity and speed, but I am wondering if I should begin to use multiple catalogs as a way of avoiding future problems with the facial recognition system if has a reputation for creating issues like I am facing.

Thanks for any thoughts you might have.

Ralph