To be very specific, I actually fostered a dog to try and help my depressed teen. I witnessed her having meltdowns when I asked her to walk the dog. She became very agitated and hated the expectation and the responsibility. Depressed is very hard to understand, unless you have experienced it first hand or even at close quarters. I have wanted to give every person who has told us all about their situation a huge hug. It all rings so true and it makes life so hard.
I don't people have piled in necessarily. It hit a nerve for many but there were other factors that people picked up on - such as there being an able-bodied person in the house who could walk the dog after 7.30. But I think mostly people have picked up on the resentment against the BIL. Now here is controversial thing - in depression you can only cope with yourself but there are certain things you can do, can cope with - and it gives the impression that you are OK. But when you have a regular thing you have to commit to - it can make you very distressed. I have seen it with my girl.
Of course I feel for the OP - poor love, she is pregnant and in pain. I hope she comes up with a solution but if the dog walking is not possible, then she does need to let it go. I am in the camp that family is great but my responsibilities are mine. I have cancer, a depressed teen and animals. I struggle a lot. My family would come down (from a long way away) to help me if I asked - but I never feel resentment. I do not expect it.
Let's all try and understand one another here. Depression can make people touchy, aggressive and they go round in circles in their mind. Exercise, good food and goals may help some but it does not touch the side with others, like my daughter.
Sleep well all of you. I hope tomorrow is a good day for everyone, including the OP. I hope that we haven't hurt you - it was not our intention, I feel. It simply hit a raw nerve for many of us and we could see other solutions, rather than the central one.