Probably the best approach would be finding out how to expand the 8Gb disk so it utilizes the full 14 Gb when its running on your eMMC.
Advantage would be that it would actually use every last byte of space 😊
I know most Raspberry Pi distros have a build in option for this, which is obviously not what you're working with right now.
I have no experience otherwise with this, but I did find this Stack Exchange post that talks about PartEd and GrowPart - maybe this is useful for you.
Alternatively, you could grab the larger image and mounting it on a Linux system.
There you can use PartEd to select one or more partitions to resize.
As for mounting an IMG file under Linux; I have never tried this, I usually work on a Mac and macOS handles mounting an IMG file automatically.
I did find this article though, explaining it like so (/mnt/disk being the mount directory you'd like to use):
mount -o loop disk1.img /mnt/disk
I hope any of this is helpful.
APB only supports resizing an Ext partition on a standard (old school) partition table set up.
Eg. MBR with standard partitions (4). So no BTRFS/GUID/Extended Partitions, etc.