FBAR filing joint account with parent outside of US

Hi,

I saw a lot of people asking about join account with spouse, but my situation is a bit different, it’s a joint account in a foreign country with my mother who is not a U.S. person and live outside U.S. her whole life.

 

I have a small amount of saving in that account before I move to US, but everything else are hers (including her income and investment gains that has nothing to do with me). I do not have foreign income or investment in the joint account. I only occasionally help my mom manage the account, like if I saw she have a credit card bill overdue, or like an accidental overdraft and I’d help her move money from savings to current account. 


Do I still file FBAR? But seems unfair if over 90% of the asset is not mine? Would IRS want to tax me on this joint account if I file FBAR? 
Is there anything I should do to avoid this?