I take Citrical at a low dose 200mg to 500mgs a day. While my calcium intake from food is good. We don't absorb the available amount. I drink fairlife milk which has 13 mgs a cup, but we can only absorb about 1/3 of that. https://courses.lumenlearning.com/suny-nutrition/chapter/12-22-calcium-bioavailability/ It is almost impossible to judge how much calcium you actually get from your diet. The advice for us is 1,200mg in a day.
The trouble for most of us is the loss of estrogen. My opinion is that the perfect diet and the perfect amount of exercise can't protect us sufficiently. I expect your sister will be joining you later on. Vitamin D is an important supplement with Forteo because the medication uses D to great effect and your levels will probably drop. Mine did. I like to keep the lab number at 70ng/mL, though most will say 40ng/mL is the best number on the labs.
I so hope you have a good experience with this amazing drug.