Aelrahc, be nice to your mum. You should try and teach her how to fix things instead of calling her "technologically impaired", not nice. Anyhow, may be there is a trick that you might want to teach her.
STOP continuing to try to charge, sync or otherwise use your phone. This potentially can make a bad situation worse. Remove the battery.
The very first step I would take is to disassemble your phone. Use this guide to disassemble your phone. Take a careful and close look at all components and connectors. Truly assess the damage. Look for major corrosion, evaluate the pins in the connectors etc,. Take a look at all connectors as well as cable ends. Use a soft brush and clean it very, very thouroughly with sterile water. Once you got the gross contamination cleaned, use 90%+ isopropyl alcohol and clean your parts some more. For a proper cleaning, use this guide. It was written for a Apple iPhone 3G but it is still pertinent to your phone as well. I can not stress the importance of a good cleaning enough, so do it over and over while replacing the alcohol after each cleaning. Do not use compressed air for the cleaning since that can drive liquid as well as corrosion particles into areas that will cause trouble later on. Do not use drinking water, if you need to use water, use sterile water. Also, you do not need to leave it to dry for a day. Isopropyl alcohol in the higher concentration will evaporate quickly and dissipate the water. The importance here is the cleaning. the best of course would be to get it professionally cleaned with an ultrasonic cleaner. Do not forget to replace the battery after you cleaned it properly. This is a must and not an option. It will fail if you do not take care of it now. Keep in mind that water damage is the hardest to troubleshoot and to repair. In your case with the "screen occasionally flashed" it is possible that you will have to replace the display to get it properly working again. Hope this helps, good luck.