Can I be reimbursed for my expenses while taking care of my mother in an assisted living home?

It's unlikely, but you can check with your state website under "aging." Search the links and look for what is offered for financial assistance. Never say never until you check out local resources.
Good luck,
Carol

What expenses are you talking about? If you are paying for your mother's assisted living, as Carol has said chech out financial assistance but what you have already paid (the past) may be quite a challenge. If you refer to expenses relating to yourself because your mother is in assisted living, your expenses will very likely not be covered. If you refer to expenses relating to handling your mother's business outside of assisted living, there is the possibility of reimbursement for carrying on in behalf of your mother. Has your mother appointed a POA and is she still able to make decisions, therefore competent.

I am looking for reimbursement for clothing, food items (snacks), hairdresser, toiletries, paying some bills from my personal account, etc. I had POA when these items were purchased.

Without considering any issues surrounding any statute of limitations that might apply, if you had POA, you had authority to make expenditures for your mother. Those should have been paid from your mother's account but regardless, they were authorized and hopefully you have the receipts. Gather all, create an invoice and submit to the current POA for payment. If payment is not received, you have legal options uncluding hiring an attorney or going to small claims court or at the appropriate time submit the invoice to the estate of your mother. Keep record and send the invoice via certified mail requiring certification of delivery to the appropriate and specific person. Mention on the invoice "payable upon receipt" or "payable within 30 days" or whatever time frame suits you.
It is advisable to send a past due notice or two prior to going to an attorney or small claims court. You can likely have success if you make the effort in a timely manner. Best wishes!