A bit of experimentation called for mate.
Around 300 inkjets are supported on the basic OSX disc and there are new drivers brewing/just around the corner.
Meanwhile the OS9 drivers will work in the new system while in classic mode. Most of the software her ladyship wants to use is still OS9 anyway - it simply hasn't been ported over yet - so she's not losing out.
If you go into System Preferences in the Dock you'll find an icon for 'Classic' operations. Dip into it and you'll find you can set 10 to boot up and at the same time boot OS9 into a protected kernel. This way you can open OS9 applications at the same time as working in the OS10 environment and they happily print.
This may all read as something complicated but it is actually ridiculously simple and works beautifully on both of my Macs.
Finally, try using some other Epson drivers - they're often very closely related in basic structure.
Rob