I always make new chins my pets before I introduce them to another chin. If they trust me, they'll trust I will not let another hurt them and will pull them out before any serious injuries are inflicted.
It's all about trust, so give her time to get to know you first.
Emma doesn't want to share just yet, you also need to show her she wont loose you to this intruder.
Take it slow, love them both , then ask if they'd like to meet.
Remember they may never like each other, so a second set up is a must.