How to make her loose weight?

I adopted Rhoslyn in November, she was 2.5 and speyed. Some time ago, the lady at the rescue (I send pictures) said she had become fat. I didn't notice really, but now I do and yes, she's F A T.
They shared with piggies for some time so she ate their food every now and then, but lately it's only pellets. And veg and hay of course. They have a lot of space to run around. How can I get her to loose weight?

how many pellets does she have daily? Cut down on them maybe?:wave: