Ex girlfriend problem

My ex girlfriend left me for her best friends husband after the girlfriend died. My ex was in the bed with him a few days after the girlfriend died. this was a year ago, and they have been together since. On an on line dating site, an aquientence of my ex came up as a 100 % match for me. Also some mutual friends of my ex and I felt that we would make a great couple. Well, we did meet, and then had 2 dates, and there is a definite connection between us. Here is the problem, she is worried about her circle of friends saying that she should not date me, as there are friends with my ex in this group. I met her younger daughter(23 year old) at dinner one night, she says that she liked me and felt that her mom should be happy and to go out with me. Haven't met her older daughter yet but she feels that there is the rule, don't date a friends ex( this case more of an aquentence). Do you think that there is a problem with us dating, seeing that I wasn't the one to break up the relationship with my ex. Help please

Thanks for the reply Susiedqqq, their ages are in the late fifties to early 60 and they met in a divorce support group. There are a couple of friends that say go out and be happy to her, the older ones don't have a boy friend, so (I think) they want her to be as unhappy as they are.