Unless this is someone who has been like a sister to him most of his life men do NOT have 'female friends'. We don't. We can be 'just friends' with a female if she is cool and fun to hang out with once we've accepted she won't sleep with us. Other than that... nope. I think you should question at least her motives if not his. I'm sure you know some men you think of as having a 'friendship' with... if they were married would you be regularly texting them? I didn't think so.
Your feelings are just that..YOUR feelings, no justification needed and your husband should respect the way you feel even if he thinks it's ridiculous. It bothers you, it would me too! Respect the way you feel toward this woman/relationship because your gut is telling you something.
If you're so uncomfortable with the situation, why don't you talk to you husband about it? You need to let him know that he needs to give you reassurance that you have nothing to worry about between him and his friend. There could be nothing going on at all....just pure friendship, but since you are supposed to be his #1....I'd say talk to him and let him know how you feel through and through.
jealousy is a normal, sometimes healthy emotion. maybe you should talk to him about it in a normal, not crazy tone, and see what can be done..
Why are you jealous of her?
He is the one you have to be careful of.