Court has allowed my Mom (92) to keep pension check. Granddaughter borrows money, pays back. Should I say something about this?

I would get a list of the amounts borrowed and when/if they're paid back (for certain, as it sounds a bit iffy), but also gently inquire of your niece why she needs the money. Is she laid off or otherwise out of work, or doesn't she work at all? Is this a long-time habit or started just recently?

As guardian/conservator, depending on the order of appointment, you probably have the right AND obligation to monitor your mother's finances, so it's not out of line to become more involved and find out if the money is really being returned, as well as why the niece needs the money in the first place.

Perhaps your niece's mother or father could offer insight into the situation, but you could run the risk of their supporting their daughter against your inquiries and intervention.

If there is financial abuse on your watch, you could be blamed and considered negligent in your fiduciary obligations.

I am puzzled as to what guardianship means to you. Were the responsibilities laid out before you accepted this role? Because at the very least, I should have thought that you have a duty to know what is happening with your mother's finances. If the court allowed her to keep her pension check, that's one thing; but it doesn't mean that you aren't accountable for what happens to the money. You're going to have to take charge to the extent that she can still do what she likes with it but you MUST be kept informed. How does her pension get paid?

This is a rights versus responsibilities issue. Since you are responsible, as her guardian, for your mother's welfare you also have a right to all the necessary information to do that. Maybe see if you can get nephew and granddaughter together in the same room and thrash this issue out with them. Because if any authorities start asking questions, you'll be the one who has to answer them.

I sent out registered mail. "No more borrowing from my Mother." That stopped it.
Also, I had to tell 2 adult grandchildren, that "No, they were not moving in with Mother." They had no intention of helping take care of her.

You live in Michigan. If Grandma needs to go on Medicaid, the funds that she is giving to granddaughter will be treated as gifts unless she can prove that she paid them back. That means that you as conservator/guardian will have to come up with any lack of funds to cover Medicaid penalty (since your mom is no longer capable of managing her affairs and requires a guardian). You need to do a more formal arrangement of borrowing and paying back than a relative writing on calendar or you will all find yourselves in difficulties if court, APS or Medicaid get involved later.

The niece plays lottery daily, likes to shop, get her hair done weekly, pretty much lives above her means. She is working and also works in a facility where she doesn't have to pay rent or pays very little. I don't understand what exactly she is doing with her finances.