I personally believe that it's very hard on a dog to be alone for 8+ hours per day. I'll admit it's easy for me to say that because I'm allowed to bring my doggy to work with me.
It sounds like either of those solutions would work out great! Who knows, maybe your yorkie will end up being best friends with the other work dog. I guess that seems like a slightly less risky approach since if it becomes a problem taking her to work, you can always get another dog, whereas if you get another dog that she doesn't welcome, you potentially have a bad situation on your hands.
I think it is very nice that you are considering her emotional wellbeing.
