The 20-year-old actress, who is the niece of Julia Roberts, said the exercise classes are great fun.
She said to Women's Health magazine: 'I started taking classes with friends as a way to both work out and hang out. You don't realise how much upper-body strength you need. It's also a good way to build confidence.'
However she also maintains a healthy diet but not just for the way she looks.
She said: 'When I was younger, I would eat whatever I wanted.' Later on: 'My mum told me to eat healthier, not for the outside, but for the inside. A lot of women feel like they have to eat healthy to be skinny, but for me, it's not about that.'