No. First of all, spells and mermaids are not real, so it doesn't really witchcraft. Witchcraft, at least the Western conception of it, is tied to the religion of Wicca. Most folklore relating to magic is not related to Wicca.
There is no such spell to turn you into a mermaid.
There have been no proven cases of witchcraft killing in the way you think of - casting a spell and the person falls over then and there. There are cases of people believing they have been cursed, and becoming sick and dying because they believed it. There are cases of people poisoning others and claiming it was a magic spell. But there is no proof that you can kill somebody by a spell.
There are no spells that will turn you into a mermaid.
If you are a mermaid you can get legs by doing the mermaid reversal spell type:22Q56J.
There are no spells that will turn you into a mermaid.
NO
No.
Mermaids are not real. They come from legends and fairy tales. You can not use a spell to make you a mermaid. There is no such thing.
You can do a mermaid spell as many times as you wish and you will not turn into a mermaid. People can not change into mermaids. Mermaids are not real and are only make believe.
You can't reverse a mermaid spell because neither spells nor mermaids are real to begin with.
There are no such spells.
You can do a mermaid spell a million times and you won't become a mermaid. Magic spells are not real and can NOT turn you into a mermaid. Mermaids are not real. People can not turn into anything. It is all make believe.