The safest approach is to reset the laptop and set it up as a new computer. Before doing so, save any files you are legally entitled to keep, because the reset will erase the existing accounts and personal information.
In Windows 11, open Settings > System > Recovery > Reset PC, then choose Remove everything. In Windows 10, open Settings > Update & Security > Recovery > Get started, then choose Remove everything. Follow the prompts, and when Windows restarts, complete the setup using your own Microsoft account. Microsoft recommends backing up anything important first and having the BitLocker recovery key available if the device is encrypted. Reset your PC
Please do not simply rename or reuse your mother’s Windows account, as that could leave personal data and account connections on the computer.
I hope this helps, feel free to let me know if you need any further help.