Why was it assumed she "refused"? Perhaps there was a biological issue there. Either way, I do not see why Oburu had to mention her in such a manner in such a public event. It wasn't fair. Up until then, their issue had remained a private family matter, neither Raila nor Fidel nor Ida had felt the need to do that to Shiru even when they divorced and after. Raila and Ida had both managed to speak positively about and praise Fidel's widow without taking hits at Shiiru. In fact, Raila acknowledged her presence at the funeral quite respectfully. Oburu should have followed that example of decency and empathy. It was quite enough for her to be divorced for "refusing" to give birth, why did she need a public shaming at a funeral of all places? And she was present? That is such bad behavior and lack of empathy towards another human being for absolutely no reason.
As to the duty of women, as a relatively "modern" woman, I have a different outlook on it. In my view, if either the man or woman is sterile or something like that, the other spouse should accept them and love them as they are. Its like an accident or illness or something. We should not drop our vows or commitment to someone that we love if we find they suffer from some disability. We all want deep down, to feel that we are loved for ourselves, and not just what we can produce. Just like men don't like to feel they are loved for the size of meat they can bring back home from the hunt, and no more. There are some women that similarly drop a husband after years if he becomes poor or no longer needed for finances, which is bad (to me). I think it's the same principle when your spouse is sterile. For better or worse, for richer or poorer, in sickness and in health, till death do us part. It's hard for many people to stick to that but I think we aspire to that ideal for a reason.
PS, Also, the world is full of children without parents. If a couple cant get pregnant, perhaps God is calling them to open their home to a few babies needing a home and a set of parents just like the two eager parents can offer.