[EVERYTHING] Theory: Daenerys is going to die. (Based on the "Prince that was promised prophecy")

I was re-watching the Histories & Lore videos and I stumbled upon this one.

It describes the Lord of light religion from Thoros's point of view. In the end he talks about the prophecy.

The facts:

• According to the prophecy the champion will reforge the sword Lightbringer that defeated the darkness thousands of years ago. Which is a terrible weapon forged with the lifeblood of a loving wife's heart, the illustrations in the video show the champion holding his dead wife.
• Melisandre believes that both Daenerys & Jon Snow have important parts to play.
• The prince that was promised is believed to be a Targaryan descendant and the only two we know of for now are Daenerys and Jon.

Now if the prince that was promised is either Jon or Daenerys, say its Jon then he has to kill his wife (which would be Daenerys probably since both of them have an important role to play) in order to forge Lightbringer.

I think that this is a very likely scenario to happen since Jon already died once and I don't think that they are going to kill him off again, it has to be Danny, they are also building a great leader character out of Jon which indicates that he will be the one sitting on the throne in the end, this will not be possible while Daenerys lives.

I also noticed something else, In the video above Thoros talks about the great other, god of darkness and ice .. Could the whole story be the result of a struggle between The lord of light and the Lord of darkness (A song of ice and fire) ... Thoros mentions that if the lord of light stops answering (i.e. loses or something) there will be an endless winter, does this mean that the realm of the god of darkness is in the north in the lands of always winter where the white walkers come from ?

In the show, when Bran goes back to watch the children of the forest create a white walker, the area was not covered with snow or ice, isn't it supposed to be ? does this means that the land of always winter wasn't like that before then ? is it a result of the struggle and war that happened between the lord of darkness and the lord of light 1000 years ago which stopped after building the wall and split the land between the god of darkness and the god of light ?