What Causes Dizziness And Ringing In Ears After Being Hit At The Joints?

Hi my friend has been having a problem for a while now. It disappeared when she was 12 but now she's 14 and it's coming back. Sometimes when she hits a joint she says she feels "fuzzy" and dizzy like she's moving. Her vision starts to turn black and she gets a ringing in her ears "Almost as if I'm underwater". Please can you help her?