Well, I was not 100% right when I wrote the previous answers. Here's couple of things you could do:

1. You could duplicate the group with the "Duplicate Input Graph" option (not the same as "Duplicate Input Connections". This will duplicate everything in the group as well as the particle shape node. This way you get two emitters, two particle shapes etc and you can control them individually.

2. You could duplicate only the particle shape node with the instance option. This will create another particle node which will behave exactly like the first one.