Hello - I'm new to the site as well, but thought I'd share what little experience I have!
My dog did the same to one of mine and she ended up with no skin on her back and two very deep gashes that I missed initially, and the poor thing became a host for maggots (ewww). She also stopped sitting on the perch and took to the nesting box - it may be because it's too awkward for them to roost, or it could be that they feel safer in the confines of a nesting box, or it could be that she's keeping out of the way of the other chickens, who seem to like raw flesh and may peck at her - chickens will hide away and try to act normally to avoid being singled out as a weakling by the other chickens. I would recommend you really check her out to ensure there are no hidden wounds and make sure all wounds are flushed out with triscrub and/or iodine and warm water. Once she is really clean, spray her wounds either with the spray-on plaster that you can get in a normal chemist (to keep the wound clean) or if you want a punk chicken (like I did) you can use the purple spray (gentian) that seals the wound - but be warned, it stays on the chicken for ages, and stains whatever it comes into contact with. Not so good when my 6 year old thought it would be good to try out on the fence, climbing frame, skateboard etc etc, but it really helped my chook to keep the wound clean, and having a funky purple chicken is a talking point!
The fact that she's still laying is a good sign - she can't be too beaten up or shocked. I found a number of stories of very resilient chickens when mine got injured and was genuinely amazed at how these little things seem to survive quite horrendous injuries!
Definitely keep an eye on her and make sure she doesn't suffer from losing her place in the pecking order and gets sufficient food. Poultry spice or a nutritional supplement may help her with recovering from the shock. As I said above, wounded/sick birds tend to hide away from the others. I found they will also fluff up their feathers to make themselves look bigger than they actually are, and by the time you notice they are suffering, they can be too far gone, so check on her regularly.
Hope she's on the mend soon.