It's not clear where the swelling is - do you mean in the front where it's puffed out?
If so, that's where her crop is, has she been eating normally?
Hopefully the experts will jump in here soon.
*eta:
Oops, I am NOT a pea anatomy expert and should have written "I think that's where her crop is."
Sorry.
What are you feeding yours?
mine free range so they eat all kinds a stuff but they always get scrambled eggs and scrambled eggs with oatmeal ,nuts and fruit or veggies, depending what is in the garden at the time.
Mine can have access to corn and flock raiser but they do not eat that much of it and prefer the stuff around the ponds and of course their egg concoctions.
I grow them sorghum
All the peas love Chick weed that grows wild here
I planted them wild flowers they love the petals and seeds they make later on
Introducing rose petals to the wee peas
i grow them watermelons and cantaloupe too