Hi Nekiwa, this is probably too obvious and has been looked at but I'll ask anyway
Have you asked your client to double check *her* time zone settings?
I was reading some search results on Google to try to help you answer your question and all I could come up with is that there is a general consensus that Google Calendar is timezone-challenged (in many ways).
As far as alternatives go, I've seen many discussions on calendaring services, features, etc. in the Project Management
forum here on VAF, so that might be a good place to start looking for more info. When you land in that forum use the 'Search this forum' option on the inside right corner of the forum (it's just above the list of threads, to the right - not the same as the search feature in the main menu) to search for 'calendar' or 'calendaring' and you should find some good starting points.
Good luck with this, I hope you're able to find a solution!