Keep in mind this is just my opinion, but I think there might be a perfectly normal explanation for this.

Many women experience a sort of sexual "coming of age" around 35-40. Women, to my knowledge, don't actually experience the hormonal peak that men do, but they do become more sexually comfortable around their 40's. Considering your age, this might be what you're experiencing.

So while you've never been attracted to women before, you may be feeling some attraction at this time due to sexual maturity. No bigs.

This doesn't mean to run out and have an affair or even that you need to confront her about it. If you don't confront men you're attracted to, then you shouldn't confront her either, in my opinion.

Should you tell your husband? I think communication in a marriage is very important. Just let him know, "So I'm finding this woman at work attractive, it's really weird."

So long story short, don't worry. It's probably just part of your sexual maturity and not something wrong with you.