How old is the battery? It may have an internal short that is taking too
much of the output from the alternator leaving very little to run the
rest of the car. Try another battery. If the current one is out of
warranty, it also means it is an old battery. You can also have the
cells of your current battery tested, but if the battery is the original
one or an old one, just splurge a bit and replace it and see what
happens. It'll cost you less than a diagnostic visit to the repair shop
anyway!

I'm guessing that she is turning on the heat and defrost.
In that case she is also kicking on the A/C.  The A/c is
used to dry the air that is blown onto the windshield.

I would suspect the A/C compressor or a fast idle mechanism.