If you could start and stop OS services from a browser that would be a horrible security hole.
Probably the best thing would be to move it to real hosting -- what happens when that hard drive made by the lowest bidder dies? Is your mysql being backed up? What if she wants to use it from her mobile phone.
Second choice would be to just configure Apache and MySql as a service on the machine. Or grab an old machine, toss on any linux variant you like and run it there. Backup caveats still apply.
Third choice would be to write a small powershell script that:
1) Check to see if XAMPP is running and if not start service
2) Fires up browser pointed at correct url