2002 525i won't start

[letsg02h00ters]

Hello, my first post and it's not even about my 1990 325i.

So my mom calls me to pick her up because her 2002 525i won't start. She tells me to bring jumper cables. I bring cables and meet her to jump her car. I hook up the cables (to the positive and ground terminals under the 2002 hood), start my car, then when I go to start her car... CLICK CLICK CLICK CLICK CLICK.

Whoa, I try it again... same 'CLICK'-ing sound. I don't think it's a dead battery because everything else electrical works. Windows, headlights, radio, alarm. Could this be a different electrical or ignition problem? How can I go about resolving this situation before the holiday weekend is over? The 525i is her daily driver for work.

Any help would be much appreciated.

[letsg02h00ters]

Problem solved...