Funeral expenses are technically estate expenses. However, since it takes longer so set up an estate and than a family would want to wait to have the estate itself make the funeral arrangements, it is quite normal for a members to pay the all of the expenses and get reimbursed by the estate. Such expenses get deducted from the estate before its disbursement to beneficiaries according to the Will or laws of intestacy.
Suggestion: since you have the power of attorney, there may be an opportunity to use your mother's assets to prepay for the funeral. I recommend consulting with a local trusts and estates / probate attorney to make certain you do not run afoul of Medicaid rules. You might also take that opportunity to see if there might be any tax issues upon your mother's death. It's also good to take a look at all of her assets and her Will at such a consultation. Such an initial consultation might even be free for an attorney looking to build a relationship -- i.e. someone you would use upon her death. Even if she has limited assets, it's worth investigating all of this with a local attorney.