I would put her on strict rest. No running, no jumping, and no jumping in and out of cars. She is still injured and it has not healed.
I am tempted to tell you to take her back to the vet, and have it rechecked. I am not sure if it is not healed because there is a serious injury, or she is just being too active. She could have torn a ligament in her hip. Any soft tissue injury such as that would not show up on an x-ray, only bone injuries show up on an x-ray. She is so young it would be a shame to have a serious injury go undiagnosed and cause permanent damage. If nothing else, they could give you more anti inflammatory which I believe she needs.
I would also start to work on reducing the bump. I would put a hot/warm pack on it, for twenty minutes, twice a day. This is to help increase blood flow which will help relax the muscles, increase blood flow, and remove inflammatory toxins. After the hot pack, I would do five minute of gentle massage. Just do little circular motions over the bump. This will also help increase blood flow and help break down scar tissue that is forming.
So until you can get her back to the vet, strict rest. When you are at the vet, if you do not think you can keep her quiet to rest, you can request a mild tranquilizer for her until she is better. To take the edge off for now, you can give her benadryl. This will make her a little sleepy. The dose is 1 mg per pound every 12 hours. Just use the human benadryl.
I hope this helps.