Have her remove the battery from the PC, it's round and about the size of a nickel. Leave it out for 10-20 seconds and put it back. Then try it again.
If it's still not working then I would next try disabling the drives one at a time to see if one of them was stopping the system. Just pull the power connector from each drive to disable it. Does this PC have a regular dial-up modem in it? If it does then it may have taken a voltage spike thru the phone line. Remove the card the phone lines are hooked to and see if it works.
When were doing some of this stuff the PC may not boot into Windows. That's OK, were mostly just wanting to see if we can make it do something different at this point.
If none of this has worked then next we want to see if the memory is at issue. Hopefully it has at least two sticks of memory in it. Remove one stick and see if anything changes, if not, put that stick back in and remove the other. Check it again. We looking for any changes at all, beeps all mean something, quick beeps, long beeps, number of beeps. If it only has one stick of ram pull it out. The PC should definitely beep with no ram installed.
Next we want to know about the video. Does the monitor plug into a separate card or does it plug into a connector in the same area as the mouse, keyboard and audio ports. If it has a separate card remove the monitor connector and look at the plug on the card, is there a plug just like it in the mouse, keyboard, audio port area? If there is another plug, remove the card and plug the monitor into the plug you found and try to start the PC again. If it doesn't have another plug then were out of luck unless she can borrow a card to try in it's place. With no video card installed at all the PC should once again beep when started.
Let us know what happens