there are a couple of thinks i tried when we got ours (they were a bit older too).
Firstly, don't give treats when they bite, they might associate treats with biting.
secondly, put a treat that lasts a while in the palm of your hand, just out of reach or just outside the cage. basically make it so that to get the treat she must sit or jump onto the palm of your hand. if she eventually stays sat on it whilst she has the treat, you can use your ear tickling trick. this might work!
alternatively, try and find something else she likes that involves contact. two of mine for example still don't like being picked up. when you've got them thay area fine. its just getting them. so i sit outside the cage and let them go up my jumper. only then can i stroke them and pick them up, after they've snuggled under my fleece!!