I don't think we can know if someone is doing anything under the guise of something else - only they can know that.
Maybe the Mrs Bucket comments were less than 'kind', but we do get a lot of threads on here that are, as Calli says, full of holes. Just because most posters on GN are older doesn't mean we are daft, or that nobody should speak up if they feel that they are being laughed at.
Why would a mother be disappointed by food provided by her daughter on Mother's day (or any day, come to that) particularly when it comes with an invitation to spend the afternoon together, and the mother was made to feel welcome? If someone posts on social media to say how upset she was, and ask whether it is unreasonable to complain to her other daughter about the afternoon laid on for her, and posters say that yes, she was being unreasonable and that she should feel happy to have been invited, they are just answering the question as it was posed.
When the OP vanishes, and the other daughter comes along telling a different story about what happened, is it unreasonable of posters to be suspicious?
As I said, I do realise that hearing over and over that you are being unreasonable can be unpleasant, but that happens on GN, as there is no expectation that people will RTFT before replying. When anyone suggests that such an expectation might be a good idea, they are told that they are being unpleasant. Also, the OP wasn't responding, so it's not as though she had come back to say that she had taken the comments on board, or offered any further information.
What about being 'kind' to the daughter who laid on soup and cake and an invitation to share her Sunday with her mother, only to find that not only was this being discussed on public social media, but her mum and sister had been talking about her behind her back and the comments from her mum had been such that the sister was 'disgusted'? Does she not deserve kindness? One sister apparently found the conversation, so why couldn't the other one do the same?