Your hubby might just be craving for attention and wants a listening ear and to hear assuring sweet words. As his wife, try to be the one giving it. Its human nature to want to hear sweet things. My hubby's business partner is a female foreigner and he is a frequent traveller. Being a woman, i get jealous too and of course led to crazy thoughts. But, we have since ironed things out and l'm very good friends, like a sister, with his business partner and very supportive of their business. Communication is very important in a relationship and so is trust. Try to understand what your hubby wants and give him.
I second about the talking to your Husband thing. I think that you should let him know your worries and concern when you are not feeling emotional about it or he will brush you off and not take you seriously. I understand that it sounds like the other woman is up to no good so maybe you can tell your Husband the things that you don't want him to do with her or just generally women. The fact is that there will be other female colleagues and clients who may seem to pose a threat in the future so I think it is best to work with the inner circle - your Husband.
I think you should have a talk with your hubby. A good sit down talk with him know how you feel. Try not to accuse him of anything as he will get defensive. It is good so that he knows how u feel and he will also know u are aware of this woman in his workplace. But dont get overly paranoid too cos for all you know, nothing is happening. Good luck!