Tubular tires are near-perfectly round, and they can run much higher pressure than clinchers.
In the past, the tubular wheel/tire combo was also much lighter than clinchers, although I'm not sure that that's true any more.
It seems odd to me that her race wheels would have non-standard hubs. Even so, I don't know why she couldn't build up new wheels with clincher rims using the same type of hubs (or even using the very same hubs, if she wanted to dismantle her tubie wheels).
On my race bike (which cost me about the same, years ago) I had tubies for racing and clinchers for training. Both sets of wheels were built on the same model hubs. (My issue with re-fitting the frame has to do with reluctance to spread the dropouts to accommodate a modern rear wheel... I'm afraid it would give me a bizarre chainline...)
but as far as your friend's bike, honestly if her bike is as old as mine, she can have a new one for the same money it would cost her to re-build it with modern components. Which is what I did, and why my race bike is now storage room jewelry![]()