Welcome To BYC
How is your Duck?
For the Tums, you can cut it in half then give her 1 piece at a time is if you wish. Tums don't mix well with water, so I give it whole or in pieces. Basically, whatever method you can find to get the calcium into her is the best method
Was she able to pass the other eggs?
If you have epsom salts, these can be added to the soaking water, but it's not necessary.
Work on keeping her hydrated too.
I'll tag in some Duck Folks to see if they can offer more suggestions. If she were mine, I'd give her extra calcium for several days even when she's expelled these.
@Miss Lydia @Quatie @HollowOfWisps