If the lawsuit settles before your mother passes, you may have authority as POA to sign the necessary papers. It depends on what was checked on your POA. Then the funds would pass through the estate. If the total is under $30,000 for all assets, small estate administration is available. A voluntary administrator has no power to enforce a claim for wrongful death or personal injuries, so small estate administration is not an option if the lawsuit is to continue after Mom's death. Most likely the law firm handling the personal injury case can assist you in filing for letters of administration if the need should arise.
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Upon you mother's passing, if the estate is under $30,000, you will be able to file a small estate proceeding and become a voluntary administrator. In that event, you will be entitled to be reimbursed for all of your "reasonable and necessary expenses" in connection with the estate and, as a fiduciary, you are technically entitled to a commission (if you choose to collect it).
If, at a later date, you need to proceed with the litigation settlement on behalf of the estate, you will need to convert the voluntary administration proceeding into a full administration proceeding. While you should be able to handle the small estate filing on your own, it may be advisable to contact an attorney if you need to proceed with a full-blown administration.
Please note that the above response is for general information only and does not constitute legal advice or establish an attorney-client relationship.