Can a man be friends with a woman he used to have feelings for before if he has a gf?

My bf is friends with a woman he used to like before me but she couldn’t recognize any feelings for him. She was there for him when he almost died because of renal failure when his family abandoned him. She helped him get on his feet and get him the things he needed when he didn’t have his papers. They are still friends now. They text and call each other ever now and then. He says that there is nothing between them and assured me that he knows how to leave his past in his past. We argued about it and he said he doesn’t drop people who has had his back like that when no one else did. Not for me not for anyone. He said you don’t do that to the people who were there for you it’s wrong and his friends agree. He says we that we live together and that he is trying to be sincere with me and that us fighting about this issue has affected him a lot. He forgot to take his life saving meds one day because we were arguing badly over this and he never forgets.