you should get an actual lawyer to have a secure will rather than rely on any online service

In some jurisdictions it’s hard to entirely disinherit family so the typical advice is to leave a token / symbolic gift to relatives you wish to exclude, rather than excluding them entirely. So maybe leave Mom’s old china or $100 to your sister (and any decendants if she predeceases you) so she (they) can’t claim they were overlooked.