Husband and coworker ? Advice

My husband has started a new job about a year ago , and has became very close friends with his coworker that’s a woman. He gives her a ride every night ( cause she rides the bus) she gave him a gift for his birthday that had “ papa with a bear on it ) so papa bear . He mentioned to me that she takes food and will share with him ... I meet her at a xmas party for work and they hugged each other and I felt very uncomfortable and out of place she kept staring at us . I was 8 months pregnant then so thought i was just very hormonal I did mention it to him and he was like I love you I was having you meet everyone she’s just a coworker she’s an older lady blah blah . But this weekend he went to the bar and said he was going with a guy coworker no big deal got home. Come to find out her son texted him and asked if his mom stayed at the bar. (Her son works with them too) He replied dropped her off already but at what point is it no ok or am overreacting?? I told him he wouldn’t like it if he was in my shoes so why is it ok especially for her son to be texting him and asking about his mom at 1 am . What he sneaks says is wow I would never do anything with her she’s much older and not attractive. And to stop saying anything like that because it makes him feel uncomfortable....

Thoughts ????

Also we do have 2 kids and a 5 week old baby .

I want to say the lady is about 45 and he’s 27 ( to me age doesn’t really justify it)