You have to be kidding!
NOS has to be the best 'Bang for buck' option on the market. Name another mod that can give between 50 - 250hp for around 1G?
If you think you can supercharge an RB and ever get it through regency (although technically you should be able to) you havent been involved in modifying cars for very long, either that or you have an excess of BUMB. A supercharged line is a defect waiting to happen, and more likely to be noticed than a line with NOS.
Another question: - why the concern about having to refill the tank? at 14lb boost you roughly double the fuel used compared to no boost, I've never heard of this as an argument not to turbo a car.
NOS is a great way to get aditional torque and power out of any motor, especially NA, and its there when you need it. My car has 250rwkw, but I very rarely use that many, so much like NOS its only there for the few times I need it.
On another note think of the money she is saving each year on insurance, it would more than pay for all the NOS you use in the year.