The pilot of the balloon reported that, while flying level, in preparation for landing, he brushed the basket in the top of a tree to slow the forward speed. After slowing, he conducted a standup landing with no basket tip over. After securing the balloon, one of the passengers reported that her foot was injured. The pilot reported that there were no preaccident mechanical failures or malfunctions with the balloon that would have precluded normal operation. The injured passenger reported that, prior to landing, the pilot announced they were coming in too fast for landing, and he was going to hit the treetops too slow them down. He instructed the passengers to assume the landing position. She then felt a "hard whiplash-like impact" and heard the snapping of tree branches. Upon landing, she experienced pain in both ankles and was unable to immediately egress from the basket. She later egressed with assistance. She declined immediate medical attention offered by the pilot at the scene, and again during the drive back to the operator's base. She elected to seek medical attention later that day and was initially diagnosed with a "bad sprain", of her left ankle. However, a follow up visit with a doctor later identified fractures in both of her ankles. Another passenger reported that, while not familiar with balloon landings, the landing "seemed hard and was a shock". He further stated that, they had not been previously briefed that such a shock may occur during landing.