Is it bad to share the same drink my mom takes her tamoxifen with for fear some residue will get inside me?

Not a risk: The amount of tamoxifen transferred by using the same drinking vessel is not likely to pose any health risk. However, it would be better to not share utensils for reasons of hygiene. For good health - Have a diet rich in fresh vegetables, fruits, whole grains, low fat milk and milk products, nuts, beans, legumes, lentils and small amounts of lean meats. Avoid saturated fats. Exercise at least 150 minutes/week and increase the intensity of exercise gradually. Do not use tobacco, alcohol, weed or street drugs in any form. Practice safe sex. Get HPV vaccine.