You can absolutely get two new hens, but you'll want to make sure to have a quarantine time. Let them see each other without having contact for a while and when you're ready to integrate them try it at night. I've had a lot of success this way. They seem to be much less ornery in the morning 
What's the climate like where you're from? That will also play into how you will merge the two groups.

What's the climate like where you're from? That will also play into how you will merge the two groups.