Generally speaking, as long as the trust instrument specifically allows itself to be restated, a Revocable Living Trust can be restated as often as the Grantor desires. Each restatement replaces the old instrument in its entirety; however, unless the restatement specifically purports to adjust the name, the original name and date of the Revocable Living Trust remains intact.
If it is a joint Revocable Living Trust, then you must look to the trust instrument to discover if the surviving Grantor has the authority to restate the instrument in their sole capacity, or if the trust instrument became irrevocable upon the death of the first Grantor.
Also, remember that a restatement replaces the entire trust instrument with a new trust instrument; whereas an amendment only adjusts specific portions of the existing trust instrument.
Your mom can have a 2nd restatement prepared using the original Trust name as long as she has capacity to do so and the underlying documents reserved the right to further amend, restate, or revoke the trust. In the preamble of the new Trust should state its history. For example, the Jane Doe Rev. Trust of 1990. which was amended in 1995, and restated in 2005 . . . Hope this helps.