thank you both for your reply

I'm not going to use agent B when agent A acutally showed us house. We are just concerned our currect agent is not familiar with areas which might be our target area. For exmaple, when we asked her if she knows any shapell homes in a certian area, she did not reply after 3 weeks, I guess she just does not know. and we feel if we can work with an agent familiar with this area and also faimiliar with the listing agents, it will work much better.

Thank you both for taking your time to reply and share your knowledge.