Calcium carbonate for osteoporosis (Tums!)

Hi everyone, My 89 year old grandmother has been taking Calmag (5000mg of calcium carbonate) for many years to treat her osteoporosis (prescribed by her doctor). Since she no longer wants to swallow those huge pills, she asked me to search for the same dosage but in a chewable, powder or liquid formula. The first thing I find while doing this research is that Tums are basically the made of the same active ingredient, would be cheaper and chewable!

I don't know if there's anything I should know about making this swap, but I wonder if taking 5 tums (to reach 5000mg) instead of those Calmag pills would be the same?

And also, from all the available types of calcium out there, do you guys think it makes sense to prescribe calcium carbonate for osteoporosis?

Thanks for your inputs! Kim