Attacking candidates don't need to explain, they'll just label her "friendly to Wall Street." She'd have to explain why and that becomes hard given that no one understands derivative trading.
That may do some damage in the primary, but since the thread is asking about electability in the general election, I'm not so convinced that's such a killer line of attack. Again, barring some easy way to connect the dots between her votes on these topics and regular people's lives.
No argument there. Without the optics of paid speeches to Wall Street, hard for Trump to argue that Gillibrand is closer to big banks