You asked about rigging boats for a 16 year old girl – here are some Rowperfect Resources which should help you out.
You don’t specify sweep or sculling so I’ve included both.
- Sweep Oar gearing for juniors part 1
- And part 2
- How to Rig a Junior16 Girls Eight
- The BioRow rigging chart where you can put in your own numbers to calculate recommended rigs.
- General articles about rigging
I hope this is useful – do let us know how you get on.