Am I in the wrong?

My dad has korsakoff syndrome, which is alcohol induced dementia. I live about an hour and a half away, whereas he has a brother and sister in law who live about a 3 minute walk away. His sister in law has been doing his grocery shopping for him each week. I've applied for lasting power of attorney, which is in the approval stages. My auntie mentioned she was going to sort another food shop out for him this week. I always say how grateful I am she's been taking care of this because it is genuinely such a relief for me to know he has food each week. I asked if she could send me a receipt once she's done the shopping, I can move money from my dad's account.

She got offended and asked if I don't trust her. I replied to say obviously I do, but I'm handling someone else's finances so would feel more comfortable having a receipt in case I'm ever audited in the future. She then made excuses that she wouldn't be able to send receipts because she does the shop online, it's mixed in with her shopping etc. She then suggested I can do the shopping if I want to monitor it (bear in mind I live over an hour away and I'm taking on the responsibility for everything else). I then explained I'm not monitoring anything, just having evidence for spend on someone else's account, which to me sounds reasonable. I backed down and said I'll send the agreed amount each week, without a receipt, but will use a reference on the bank transactions.

I later messaged her to get her bank details to move the money as agreed, she replied back to say 'don't worry, it's fine' which made me feel uneasy. I responded to say that I want to pay her for the food, and I'm sorry if I caused any offence with asking for receipts. She still hasn't replied after a few days. I really didn't mean anything by it and to me it seems reasonable when handling someone else's finances (especially someone who lacks mental capacity) but her reaction has made me question whether maybe i was in the wrong to ask in the first place.

What do you think?