Computer Science major looking for guidance

Banks seperate IT and market making. CS degree would only be particularily valued in trading at a prop shop. In Banks, the trading infrastructure is built by IT (some of whom get paid very well) away from the trading floor, and real-time analysis is done with vba programming. On exotics desk where computation can be too extensive for VBA, people sometimes code DLLs in C++ and call them from VBA, but this isn't a big part of the job and quant developers are always adding new code to the "central reserves" that allow traders to price stuff on the fly by calling it from VBA. At high-frequency prop shop/HFs, there is a little less distinction between IT and traders since the actual trading strategies can be very dependent on algorithms IT produces. Banks also have prop trading groups hidden away that do HFT and thus require high-level CS background of their traders, but they typically hire those people from either top performers in prop shops/HFs or sometimes take chances on new MS/PhD grads.

That said, a CS degree is still great and obviously more relevant than many other degrees that get jobs on the trading floor at major banks. But for jobs on the trading floor, CS majors aren't much more "qualified" than a VBA-competent non-CS major. If she really enjoys CS and wants to make direct use of it in trading, I would advise her to get a job at a top HFT prop-shop. (keyword "top"- e.g. Getco).

note: this isn't my area of expertise though. My fiancee has experience working as a quant developer at MS in the early 2000s, and this is what I remember from her explainations. I imagine things are always changing. Use Wilmott as they are more familiar than this forum.