Yes it does change the meaning of the work. (There's a fine tradition of this in the arts, most famously around the work of Duchamp but less obviously with many others through history.)

Personally I've never liked Charging Bull as an artwork - tis' too propagandistic for my taste, and I think the creator half-assed it by not exploring the equally powerful concept of an angry bear - and then we wonder why people on Wall Street profess surprise and helplessness in times of recession.

I think it's an interesting modification to the work to confront the bull with a human female; not only does it finally balance the work, but by choosing an oppositional figure whose identity is rooted in self-awareness rather than atavistic force, it refutes the abdication of moral agency that underpins the business culture of Wall Street. Assuming it's not destroyed by vandals, the new work has the potential for historical significance.