She took the pictures in Svalbard but polar bears are known to kill their cubs for food if everything else fails.
The actions are not common and have not been filmed often.
"This type of intraspecific predation has always occurred to some extent. However, there are increasing numbers of observations of it occurring, particularly on land where polar bears are trapped ashore, completely food-deprived for extended periods of time due to the loss of sea ice as a result of climate change," she told BBC News.
Jenny was on a boat with here telephoto lens but did not realize the bear hd its cub until she was close.
"As soon as the adult male became aware that a boat was approaching him, he basically stood to attention - he straddled the young bear's body, asserting control over it and conveying 'this is my food'," she said.