Theresa May is a rubbish dancer. She has no natural rhythm. As someone pointed out earlier, she is also a Type 1 diabetic and need insulin injections throughout the day, which have to be balanced with her carbohydrate intake. She will be making checks on her blood sugar levels before any engagement which is likely to take time and involve her increasing her activity levels.
I'd say Theresa May is a lousy dancer, (and knows it) but a jolly good sport, and a fine ambassador to join in and the criticism of her skills is totally unfair. If this is all her opponents can come up with to get at her, I'd say it's quite shameful.