Provide a
possible mechanism why folate can mask vitamin b12
deficiency.

Folate is bused to treat vitamin B12  deficiency.

Vitamin B12  deficiency causes anemia that affects neurological system and higher level of folate helps in preventing anemia by preventing deterioration of brain cells.

In B12 deficiency, folate cycle get disrupted that affects regeneration of methylene-tetrahydrofolate which is  required for the synthesis of thymidine for DNA replication. Folate is trapped as methylfolate and causes folate deficiency which demands for the supply of folic acid.Folic acid is recommended to a B12-deficient patient, as it allows the reduction of folic acid to dihydrofolate and  further to tetrahydrofolate which removes the blockage of folate. this helps in the masking of brain cells to get deteriorate due to deficiency of B12.  

Like this Folate can mask vitamin B12 Deficiency.

yes and no depends if she cut her ginger deep