My Daughter Is 14and Has Been Having Episodes Of Passing

My daughter is 14and has been having episodes of passing out the cardiologist says echo and heart monitor where normal have her drink more water she drinks plenty and only water he continued to scold her bcz she wasnt urinating in school she refuses to use public bathrooms i was like that when i was younger he said there was no more to do it happened this past saturday she states she gets a headache sees black and then finds herself on the ground she is actuve dance cheer tumbles flag football not over weight 5ft6in 129lbs i want to take her to see a electrophysiologist question pots syndrome she has low bp 90/60 i give her extra salt iam concerned and the cardiologist just thinks i want her to be sick iam a nurse and know my stuff so we git into a heated conversation he said hydrate her she is a teenager they dont listen iam concerned i recieved emergency pacemaker in jan for atrial fib and an ablation on tikosyn and still have lobg hours of hr of 198 so what maybe your recommendation