I think she's nice but I don't know what's wrong :(

I'm not sure if this the right place to put my question
I have a friend, she's actually my cousin .. she's nice and we have things in common to talk about when ever I see her
the thing is I always feel tired when I talk to her !! .. I notice that three years ago .. either small talk or long talk I always feel tired and exhausted .. I have never felt that with anyone before .. and nobody else feels the same as I do !!
it's like she takes my energy .. it's really weird because we just talk !! .. and i feel really tired after it and i need to lay down for hours sometimes
do you have an explanation for that?
I stopped talking to her right now .. it's sad because she thinks that there is something wrong with her :(