She will need to be assured the new dog will not attack her. I'd make sure that the new guy doesn't get in-her-face too much when they first have contact.
I should have also mentioned, try to be really calm and relaxed when you are doing this. Take some deep breaths and do whatever you need to in order to clear your mind and be the calm leader, picturing in your mind that things go well. Direct the person who brings the dog to stand where you say, etc., don't be afraid to take charge. That is what the dogs need to see, that someone is leading the show, calmly. Try not to be nervous because dogs can smell if you are faking it.
Even though you are meeting that dog in anticipation of adopting it, do not make a big fuss over it in front of your dog. You should probably meet it and decide if it is the dog for you before ever trying her with him. Fuss over it then.
Let us know how it goes!