My main issue with this entire situation is that he is trying to get her to go directly from one relationship to another. If she is in an emotionally difficult situation, then more than likely she does have emotional clarity about what she wants in the future. Hence my comment about being predatory - he is putting pressure on her during a difficult time. Whether or not he means it as pressure is irrelevant.
Wanting what's best for her is one thing. Trying to influence her perception about what is best for her is another.
I don't doubt that you both are overall good people who want her to be happy, I just don't approve of the method you chose to use.
I also agree that this is a wonderful opportunity for the two of you to talk about polyamory/open relationships in general to see if it is something that only came up because of the situation or if it is something that you may want to pursue anyway.