Can't help with baggy tummy other than mine took a year when I had my children

I'm sure someone will be along with advice for you.
My cocker is 16kg and is fine, but I do like them not to be skinny

It will also depend on how tall she is

My Bailey is 15.5cm. Not long ago there was a thread about height v weight. My other cocker is only tiny and weighs just 8 kg

Jo