I checked the twitter videos and there’s nothing to suggest she was shoplifting. She starts off by walking to the till with a receipt to return something. No audio recorded so people are just making their own narrative up as to how the conversation went. The later videos show The Guardian article video from other angles, plus there’s an extra video where they’re both slapping each other. The videos recorded by a witness really show the size difference.
Even if she was stealing, the shop staff need to have a proper protocol to deal with suspected theft. An “anything, including strangling, goes” approach isn’t a good look. It’s fine saying shoplifters deserve whatever comes to them, but what happens if they choke someone who they wrongfully suspect of theft ?