Hi Monica,
If folks are Vegan and not eating a balanced diet they are typically deficient in complete protein, iron and B12. As a nurse you could discuss supplements with her such a iron or a B complex. You could also request a referral to a nutritionist/dietician for meal planning support. For her heavy menses - further work up with her Primary Care Provider or GYN are indicated.
Remember the physiology here - she already is likely depleted due to low B12 and iron and now she's having heavy menstruation. Both iron and B12 are needed for red blood cell production so she's not "making enough RBCs" and she's bleeding - a bad combo. We need to get her body optimized to produce RBCs and address the bleeding.
Is that helpful?