Do the others have it too? (the lump)It is on both sides. She is so slow in wing growth, but keeps up with the others, eating well and pooping normally.
Sometimes chickens grow at different rates, and sometimes their feathers grow at different rates, but as long as they are healthy (active, eating, drinking, pooping, not being chased away from the food) you usually don't have to worry.
For feathers growing slowly, she might just have the "slow feathering" gene. That won't hurt her, but it will cause her feathers to come in slower/later than the other chickens get theirs. Once a chick finally does get their feathers, that gene doesn't seem to matter any more.