Was Willow with other goats before she came to you? I assume you just have Willow and her kids? I have alot of goats, so obviously my situation is different ....but the adults are always kept in pairs. Even when they have kids, they stay together. The only ones who live on their own are the intact males, because of fighting. But even they live alongside each other, and therefore have company.
It sounds like Willow has come to rely on you for company, and knows if she bleats you will be there to make a fuss of her. She sounds to be well cared for, and has food and water, so no worries there!!
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You will either have to put up with the bleating, or try another goat (castrated male will be ok), Perhaps if you could have one on trial to see how they get on with each other, and if the bleating stops, before you committed to having another goat, that would be an idea.
Goats are herd animals, and like to be with other goats. I think if I took away my goats companion and just let her with kids, I would get alot of bleating