Not only checking the sugars, but if low she needs to eat a low carb snack with a little protien. She should probably eat that anyway before that kind of intense exercise. If that doesn't resolve the problem I would contact her doctor.

Is she checking her blood glucose before and after exercis? She should be, as her routine sounds as it if is quite strenuous, and as a diabetic she needs help in planning what to eat and when to eat. If she finds her blood glucose is dropping, she should immediately eat or dirnk something sugary. Not too much, just half a glass of orange juice will do it, or the easist to carry are the Dex glucose tablets, These can be bought at any phaarmacy in tubes of 10, or in a bottle of 50 at walmart and possibly at other large stores. She should take 2 or 4 ofo these tablets if she sees her blood sugar is very low.. Also she need to have a special diet as a diabetic for exercising. She may need to have some carbohydrates before exercise, such as an apple, banana, or other fruit. She could also use the snack bar granola or nuts to give her enough to help her blood sugar cope with the exercise. She should perhaps talk to her diabetes doctor or nurse and maybe a nutritionist. Hope she finds an answer. It couod be that the shakiness is noto at all to do with low blood sugar, but the only way to find out is to test the blood levels before exercising. good luck in getting this sorted.

Take her to see a Dr. Sounds like shell have Hypoglycemic attacks. She must always test & record her readings. She must also have snacks with her. Feeling shakey & fatigue are symptoms of a Hypo. Remember she uses up her energy as she exercises, which should be replenished.

I find protein helps eg nuts or some cheese.

Nuts are great. Full of protein. Just make sure she eats some carbs & protein before working out.