Battery acid burned through her gullet (oesophagus) and into her lung, causing agonising pain and putting her life in danger.
Doctors say her case is not unique – about two UK children a year die from swallowing batteries.
Button batteries are used to power many gadgets and toys that will be opened as gifts on Christmas Day, experts warn.
They can be found in gaming headsets, fitness trackers, some robotic toy bugs or fish, key fob finders and light-up yo-yos.
Festive lights, flameless candles, TV remotes, singing Santas and musical Christmas cards and jumpers may also contain them.