Before the question- No they are not paying me, No I am not a modder. I was wondering cause I was given permission to go onto someones account to help them out. I have not done this yet, because I know how strict rules can be about passwords and such. I did read the terms but was unclear if this is still not allowed even if given permission and they are not paying me. Either yes/no thank you for the response.
I see other YouTubers doing this to review weapons but would I be banned if I was helping her playing on her account?
Bungie will not ban you for breaking Xbox or Playstation's ToS which does prohibit what you're discussing. However, do take note that if someone logs into your account and makes changes that you don't like or if that person logs in to your account and does things using your account that do break the rules, you'll have to deal with it. It's your duty to keep your account safe and secure, and if you fail to do so by giving it out to others, then you accept all liabilities of that choice.