Yeah, there was a fluke to that bike part. Exchange that thing and inspect and/or ride it down the aisle. There's not too much on a coaster cruiser to eff up, as per walmart build quality, a cruiser is probably one of the best things to get from there. I wouldn't even go as far as repairing the crank, I'd just get another crank, plus with the 100s of other ones, it'll then be a bit easier to find if stolen.

Ashtabula cranks are extremely common, if you want to keep the bike; replace it.

Or Exchange it.

Both the cheapest and convenient alternatives than buying specialized tools to repair a part as common as flies on an $80 bike she may grow out of in size or interest.