My freind doesnt know i know

Hi, I am 11 (some of you may have read my other post) and i have an adult friend who is bipolar..  The problem is she does not know i know. I esentually worked it out for myself after she twice came and got mad at me, for no reason i could see. after spending a while in confusion and upset i decided to try to work out why she did it becasue it was so different from the way she normaly acts.  I have spent almost two months looking up info on bipolar and when i was sure i talked my friends friend about what i had found out. and yes she does have bipolar. it is really hard soemtimes though becasue i want to tell her i know so i can help. is there any way i can help without telling her i know? is there any way to show her i care when becasue i am  so young it is hard? And is there a way when things do happen i can make my self relise it is not her but the illness?  Apreciate any coments any advice would be apriciated.