Yes, it is worth bearing in mind that some colleges have higher application rates than others, so for example your dd might be competing for a place against 20 prospective students at one college versus 15 at another. Since she does not have a particular college in mind, she could make a tactical choice based on application rates from recent years (I believe these numbers are available).
There is the pool system, where a student who has been made an offer for their subject but not for their chosen college can be made an offer by another college with places still available. This helps balance out the different application rates somewhat.
It’s also worth looking at which academics are associated with which colleges, and particularly who the directors of studies are for economics. Its somewhat helpful if your dd’s specific interests are a good match for her DoS’s, though it isn’t essential.
Different colleges are different sizes, in different locations, with different vibes. It’s worth visiting if you can or, if not, having a good look at the prospective students sections of their websites. Would she rather be in the centre of town or further out? How close is her college to the economics faculty building and library? Is she excited by the idea of living in a traditional courts and spires setting (bear in mind first year accommodation is not usually in the old courts) or would she like a modern feel (often with better plumbing!)
Lastly...it doesn’t matter all that much. I picked my college because I was very excited to work with a particular DoS...and arrived to find he was on sabbatical! I was a bit disappointed at first, but my replacement DoS was excellent, I still had a great time and enjoyed my studies, and the professor whose work I found inspiring supervised my dissertation - by which time I was more prepared to get the most out of the experience. So don’t worry too much about making the “right” choice - it’s not so very important.