Has your mother fined a renunciation/disclaimer? To do this properly, these have to comply with federal and state law. If mother has filed a proper renunciation, then she will be treated as if she died before your brother and the property would pass to the other beneficiaries named in his will.
If your mother does not do a proper renunciation, she can still give her share of the property to anyone else. This could be accomplished via a quitclaim deed between your mother and the other beneficiaries. With that, a new deed could then be prepared from the executor to the beneficiaries directly. However, your mother would have gift tax consequences.
If your brother died less than 9 months ago, then your mother needs to talk with her CPA or financial advisor to see if a renunciation for her would make sense if this is something she wanted to do.
