I think that you should fully support your daughter's ambition to break a Bonneville record. From looking at the record book, it looks like the 100cc PP is a soft record at 66.7 mph. With a little tweaking, and if your daughter has a small frame, that record would be easy to break. As a teenager I used to go down the freeway at well over 70 on my stock 1967 Honda CL 90. From there with the same bike, you can go on to other classes (like the P-AF at 42 mph). That being said, the salt is not like the asphalt.
There should be plenty of used bikes you can buy for under $1000, do some legal modifications to carbs, gearing, tires, etc to make it go faster than stock. Are you a mechanic?
So just settle on a bike as the platform and then come back here and ask how to make it go faster.
Don