Chicken lays shell less egg.

Do you know how old your chicken is, how long she has been laying? Does she lay eggs with regular shells? Is she on some sort of Layer food? Most places that sell chicken feed or livestock feed will sell oyster shell. If you want to make your own, breaking shells up into various small sized pieces should work, they don't need very much of it, so you may not see her picking much of it up. If you want, occasionally you could break it up smaller and mix it up in her feed and wet it all down, most chickens will eat wet feed like a mash pretty happily, or mix the shells in something you bake, or scrambled eggs etc. A lot of people also bake and crush up the egg shells and feed them back to the hens.
Shell less eggs are pretty common with new layers and older hens will lay them occasionally especially when starting up again after molting, various other things like stress, can bring them on. If they are just happening occasionally they are usually nothing to worry about. Occasional ones or ones from new layers are usually not related to a lack of calcium as such, but are just a glitch in the egg laying system. The membranes are added in the step just before the shell gland, the "egg" is just moving thought the whole system faster than it should. Sometimes they seem to skip more than one step. If it is happening a lot, if she never lays regular eggs, or if more of your older birds are doing it, you probably want to look at other causes. The Poultry Site has a list of possible causes ...
http://www.thepoultrysite.com/publi...ndbook/16/thinshelled-eggs-and-shellless-eggs