This is almost certainly a VirtualBox issue, rather than a distro specific issue since you are running Fedora inside a VM.
You will need to install the virtualbox guest additions package into Fedora. First step is that you will need the development tools which you can get with sudo yum groupinstall "Development Tools" .
Once those are installed you need to attach the virtualbox guest additions .iso file to your VM CD drive. You can do that on the VM Devices menu. Then mount the cd drive. Finally look for the VirtualBoxAdditionsLinux.run file and run that as sudo.
Virtual Box guest additions includes all the additional drivers required to allow the guest VM to run at it's native resoloution.