"Where did I go wrong?" You opened your mouth! :rofl2:
If she is interested in auto mechanics, then I'd let her do the head job. Walk her through the process and let her pull the wrenches and let her lift the head off of the engine.
There's nothing like having a head pulling you into the engine compartment to make you rethink why your choices - especially if you smash your finger between the head and the exhaust manifold.