The reason I suggest calcium citrate is because it's easiest of the three different forms of calcium to absorb, and in a crisis, it's speed you want. Tums is calcium carbonate as is oyster shell and bone. This form is the most difficult to digest, so it isn't my first choice in a crisis. But Tums will work in a pinch. It's important to get some form of calcium into her now so it can start to work. It can be a life or death matter.
You can shop for the citrate form later.
You can shop for the citrate form later.