poorly hen please help

Hi, i am new to this site and i have already gleaned lots of information and help. ive had 6 hens for 4 weeks. i got them point of lay, all have been doing beautifully, 5 eggs every day. They have access to layers pellets and plentiful water. I give them greens everyday, a handful of sunflower seed and occasional grapes!They freerange in the garden all day . Late this afternoon i popped out with a handful of said sunflower seeds and noticed that i was mugged only by five of them. Naturally i got into a blind panic and thought one of my babies missing! I found her in her coup (a wendy house with a mezzainine!) in a nesting box, none of them had ever done this before. I left her. half hour later she was up and about. Her rear end and feathers are drooping down she looked uncomfortable, she looked to be continually straining. She has had diarrhoea- small amounts. Her abdomen feels distended, shes very listless, she seems to be in a lot of pain. Ive given water with a bit of calcium. On advice from a chicken keeping friend (he believes her to be egg bound) i held her hinquarters over steamy water and applied ky jelly to her vent. She appeared to collapse and lay quietly in my arms i thought she was dying. it was awful. i cuddled her for a bit, talking to her (as you do). she picked up after a bit and started walking about still straining she had water. she eventually made her way outside and put herself to bed. Im seeing a vet first thing in morning, i hope she be ok. is there anything else i could or should do? many thanks
vic

thanks debbie, i appreciate your help x