Sexy older female coworker

I am 27 years old and need some advice regarding how to proceed forward in a relationship with a married female coworker who is 41 years old. She has two kids who are 20 and 15. Over the past couple of years we have become very good friends. In the past when we have had a few drinks together we have held hands and we have rubbed against each others bodies in public. She has called me when she has been drinking and she has texted me to come to office parties outside of work. She has a great body and is constantly mistaken for being in her 20s. She has told me that she wears thong panties. I am a 27 year old virgin. I am attractive but want sex to be special. She has told me about her relationship with her husband and about how she is unhappy. She doesn't ever seem to want to have him around and seems to like it when he leaves events, heads home to bed, and she can be without him. We have never taken the relationship to the next level. When we are at work we have never discussed our relationship or behaviors outside of work. Is this normal? What should I do? I am very attracted to her. I really want to have sex with her. How should I bring up the subject and ask her about taking it to the next level?