in times like this... always remember that google is your best friend . and if the files are confidential, always encrypt them first before uploading. you can then sms your sister the password separately.
How big would we be talking about for each file? If less then 20mb, you might as well use GMAIL. Each gmail allow you to attach file(s) up to 20mb in total size. She can then be at any location in the world with her notebook or at a internet cafe to download what she needs. The only problem would be getting a fast broadband to download those huge files. I use that very often now to sent artwork(s) to all my oversea offices. If I have multiple files that in total exceed that maximum space...I simple divide them out and sent out multiply GMAILs instead. And best part...it is FREE!.
Of course this will not work if each file exceed 20mb in size.