Is your concern about an over dosage?
[Since B12 is a water-soluble vitamin, it’s generally considered safe, even at high doses.

No Tolerable Upper Intake Level (UL) has been established for B12, due to its low level of toxicity. UL refers to the maximum daily dose of a vitamin unlikely to cause adverse side effects in the general population.

This threshold has not been set for B12 because your body excretes whatever it doesn't use through your urine.]

[Though doses of up to 2,000 mcg of vitamin B12 are considered safe, it’s best to speak to a doctor to find out whether taking a supplement is necessary.

Most people can fill their B12 needs through a healthy diet. Some, such as older adults or those with certain dietary restrictions, should supplement.]
How Much Vitamin B12 Is Too Much?

Or she could take a whole pill every other day..
Often we don't absorb all that is in the pill anyway..
older persons usually absorb less of most nutrients..