If she is a frum lady she will understand.
Just tell her that you and your wife discussed the matter and you felt it wasn’t ok.
If she asked one time when she was stuck- I hear.
But to ask a man for a ride to work every day is totally inappropriate.
She can bus or taxi. Or get a ride with someone else.
Do not through your shalom bayis and neshama out the window
” leshem shamayim”