Can the SS office take money out of a joint acct if two owners were not married or related in any way?

Can they? Well, they have. So that answers that question.

Next question: what does she want to do about it? Does she want to claim back the money? Or does she want to make a formal complaint, if for example they did this without giving her notice of the withdrawal?

I think the November 2 check was ok to keep as this was for October. But if a check was deposited in December that will need to be refunded as it is for November’s care.

I’m surprised it took 4 years but maybe it took them this long because the checking acct was joint? Did his estate just settle as well?

You will need to find your bank statements for that period and prove otherwise to them.

She is very upset - her account is now overdrawn with no notice and 4 years later???

If he died November 3 friend does get to keep check dated Nov 1, thats Octobers payment Now if friend got a check that came in Dec, that check gets returned because the payment is for Nov and the person died in that month.

Friend needs to contact SS. I would go to the office with proof of death and deposit info.

this check was received b4 he passed

He literally dies 2 days later - he paid bills with it and had a massive heart attack 2 days later - the check he sued was for the month before he died I'm assuming -

The Social Security Administration website states:
https://www.ssa.gov/planners/survivors/ifyou.html

If the deceased was receiving Social Security benefits, you must return the benefit received for the month of death and any later months.
For example, if the person died in July, you must return the benefits paid in August. How you return the benefits depends on how the deceased received benefits:
For funds received by direct deposit, contact the bank or other financial institution. Request that any funds received for the month of death or later be returned to Social Security.
Benefits received by check must be returned to Social Security as soon as possible. Do not cash any checks received for the month in which the person dies or later.

So "YES", the SS can and will take money out of the account that the SS check was deposited in.  Since the account was a "JOINT" Checking Account--both the friend and the roommate were owners of the checking account and since that is the checking account that the SS check was deposited into, then SS had the right to "take back" the SS check from that account.  As to why SS took 4 years before they took back the SS check money, maybe they were not notified that the person had died until 4 years later.  It is not SS's fault that the friend's checking account became overdrawn when the SS check was taken.

Yes they can do that. Did she spend his social security money?