It is alleged that Mrs Buttercup was born into the bovine community, but went to Thailand for a species change, and is now self-identifying as a human being. However, many Catholics refuse to recognise the possibility that a person can change their sex or species, quoting Jeremiah 13:23's Can the Ethiopian change his skin, or the leopard his spots?
"None of that 'Silly old moo' stuff!"
In general it is possible for a cow to lead an interesting life standing round doing nothing - after all, many bishops manage it - but some do feel unhappy in their skin. Although a diet of grass is totally vegan, and said to be very healthy, scientists claim that it causes emissions contributing to climate change. Also it is nearly as boring as tofu.
A DNA analysis of Mrs Buttercup would definitely indicate that she was a large domesticated ungulate, but she claims full human rights, including the right to bore people on Good Morning Britain, and the right to use ladies' toilets (rather than leaving cowpats in the street); also, she claims the right to pester our totally underworked police with frivolous complaints, although they appreciate these as being far less trouble than burglaries and stabbings.
Trans cows also claim the right to take part in women's sports.
Incidentally, a cow's preferred pronouns are Moo and Muh.