It’s a coin flip unfortunately and a sad fact of mechanical life that bolts (especially ones involved with the cooling system) may freeze in place and break off during removal.
If the water pump has failed then you have no choice but to proceed with the process and repair the damage as necessary with one exception.
That would be dependent upon the full story about the water pump replacement. If the pump failed and the engine was severely overheated and frying like bacon in a cast iron skillet then maybe a further examination of the engine would be necessary before replacing the pump.