I have already tried restricting the time my 3 yr old daughter spends with her to those times early in the day when I know she is sober.
When you say - tried - did this attempt fail?
I think thinking in terms of – permanent - might be your emotions speaking.
Have you thought at all about attending al-anon for yourself?
Have you given any thought to only allowing your mother to visit your daughter in your home instead of at hers? Your house your rules, her house her rules.
You can set boundaries that are not attempts to control her drinking but rather rewards for healthy behavior.