Welcome to the Forum!!
So you've had her for nearly a year and only wormed her when first arrived?
Did you check her after that worming for any worms left alive she was passing?
She has been on the same field the entire time?
Any other animals share that field with her?
If so how do they look?
Flies can transmit worms of certain kinds...other livestock in the area?
My gut reaction though is she has a bloated look to her, is underweight in that picture shared.
Her coat is just not quite right either.
She shouldn't be fat but she is a under where I would want to see her, and yes I get growth and gangly looking but she just looks wanting for a bit of something.
If you can get a fecal you would know what if anything to treat her for since not all worm medication works on all varieties of worms.
I would make sure she not have bot eggs on her coat as its that time of the year and yes she can get wormy is she ingests any of the eggs..
Then after a hard frost if you get them use worm medication that will kill off those worms which are seasonal specific pests.