What Causes Dizziness?

My daughter is 20 & lives away from home while attending college. I spoke to her a few minutes ago & she told me that this morning she felt dizzy while in shower & lost her balance. This was after going to gym & lifting weights. (not cardio) She said she still does not feel well & has not eaten much today. My concern is that she is vegan & maybe could be B12 deficient. I told her to make doctor apt asap to have blood work done. About 2 months ago she had blurred vision for a day & the next day eye specialist said everything looked fine. For about 8 yrs she has been having tingling & pain in her legs. The neurologist did test on her about 6 yrs ago & said leg nerves were fine. Could these symptoms combined be a bigger problem?