Usually, our group management service is handled more like an actual in house file server setup. While you can absolutely have storage space allocated to particular users as you have found, the standard way of handling this would be to have all data housed in your admin account, and then have this shared to your users. This way, you do not need to worry about allocating storage to particular users, and have direct access to the folders within your own account.
The time that you gave to upload 3GB is definitely slower than usual speeds experienced by clients on DriveHQ. That being said, if she tried uploading the 3GB all at once, then a mapped drive would not be the best option for this. Mapped drives are meant for more easy-access casual use rather than larger transfer tasks. When users try to upload/download more than 1GB at a time, we recommend using either our FileManager software or an FTP client. These tools are designed to handle larger tasks, whereas a mapped drive is designed for convenience.