Glad that she laid the egg. Repeat the calcium every 24 hours for several days until she is improves.
B12 alone is not that valuable for chickens. Some people mistakenly think that B12 has 12 different B vitamins, but only has B12 (Colbalamin.) Much better is human B complex. It has all B vitamins, including thiamine, riboflavin good for chicken leg problems, niacin for duck deficiency, B12, and the others including vitamin C. I get the super B with extra thiamine, but the regular B complex is fine. Any excess is excreted from the body. Vitamin E is good to have around for neurologic problems and wry neck. I would always keep those, and some calcium citrate with D3 around.