You are the one who pays the pharmacy counter, fills the gas tank for the drive to the appointment, and buys the grab bag of supplies on the way home. Each receipt feels small. Together they decide what your mother's home costs your household, and most families never write them down in one place until someone starts asking who has paid what.
Local option: New Plan Care gives families in the St. Louis area in-home help so a parent can stay home: companionship, help with bathing and dressing, meals, and overnight care. Call (314) 405-0887.
Start with what you are actually carrying
Before any sibling talks about splitting anything, list every outlay from the last month in four columns: date, what it was, who paid, and whether it came from Mom's money or yours. Include the small ones. Parking at the clinic, the mileage on your own car for her errands, the package of adult briefs, the phone line she uses, the replacement lightbulbs. Do not decide yet which ones count. Just get them on paper so the total is real.
Sort every line into one of three piles
Some costs are hers: they come out of her income, her account, or her insurance, and you are only the person sending the payment. Some are shared family costs: the things the group agreed to cover. Some are yours: the gift, the extra trip you chose to make, the snack you bought because you were there. Write the pile name beside each line. If you cannot name a pile for a line, bring it to the group first, because it means nobody agreed to it.
Check the money that comes back
Ask whether any of the lines can be paid from her account, reimbursed by her plan, or claimed through a benefit she already has. Ask her pharmacist or her benefits office what the copay and the refill timing actually are, and ask whether a plan covers equipment before you buy it. You are not looking for a clever trick. You are looking for the line that should never have come out of your pocket in the first place.
Decide how the errands get counted
An errand has three costs: the money spent, the miles, and the hours. Hired or in-home non-medical help can pick up a prescription as an errand and give her a reminder when a dose is due, and that job has its own hourly line. Decide now whether a sibling's afternoon of driving counts as a cost line, a time credit, or nothing at all. Write that rule down, because the argument later will be about the rule, not about the gas.
Make the ledger a shared sheet
Put the four columns in a shared spreadsheet or a plain notebook that lives where everyone can see it. Add a row each time anyone pays, even if it will be reimbursed later. Settle on a schedule you pick in advance, a monthly date works for many families, and settle the balance in one transfer rather than a string of text messages. The ledger does not decide who is right. It shows where the money and the labor actually went, which is usually the fairest answer any of you will get.