What is considered too far for flirting? Married wife flirting at work?

I am concerned abiut my wifes over flirtacious behavior at work..we both work at same place. We been married for one year and love each other deeply. Now before I continue I have to say this, my wife is the sweetest woman ive ever met. She doesnt have high self esteem but she tends to let every woman and man get in very close to her..i dont think she is sometimes aware if this..when I work I have plutonic friends..i will smile at fellow guys and girls and cinversate briefly..but.it stays at that..i come straight home to my wife and thats it..i have no desire to conversate with co workers outside of work..however my wife is very attractive and tends to have alot of guys talking and givivng her excessive eye contact..this one male co worker is always around her, he always looks for her, and sits and has lengthyvconversations with her..abiut a month ago she neededba ride home, cause we work different hiurs..i found out.this guy offered her ride home and she accepted..i was furious..she blows it off as nothing serious, and turns around and accuses me of being insecure and not.trusting of her..she claims she is.only in.love with me and only faithful to me..i believe her...but again still with me showing this great displeasure to this man, he continues to make small talk and eye contact with her and she still allows him to enter her circle and conversate..it makes me feel uncomfortable, especially since I told her how.i feel..we fight and argue abiut this..she is.really not the confronting kind of person and doesnt.know.how.to.tell anyone, dont talk to her like that, that she ia married..he knows we are together, and always looks to see if im looking at him..i havent talked to him peraonally cause I dont want to start problems at work place..does she like this guy or what?