@VINT64
"waiting in the wings" from Cambridge Dictionary:
wait in the wings. If someone or something is waiting in the wings, they are not yet active or important, but are ready or likely to be so soon: The team has several talented young players waiting in the wings
the girls' mom probably followed the young couple on their date to keep an eye on her baby girl but didn't show herselfedit: I missed a line and didn't notice.
the mom heard noises outside when the young couple got back and overheard her daughter say "just for today" and was confused but ready to help her baby girl hence, she was "waiting in the wings" ready to pop out at a moment's notice should her daughter need it. or to just squee about happy to have some grandbabies coming her way~