I know nothing of either college (or, in fact, anything about any college regarding music), but I'd say that depends entirely on her personality and desires.

Being on the low end in a high pressure school will cause a certain type of personality to really ramp it up, and improve dramatically.  It will cause others to collapse, losing all faith in themselves and a total loss of interest in whatever was causing the stress. If she's that type, she might very well drop out of college entirely, as well as violin, and if you forced her into it, you'd have a quite rocky relationship with her for a while. (Possibly a long while.)

On the flip side, being the best is not likely to improve her much, nor is she likely to be pushed by competition from her classmates. She'll enjoy it more, but probably not progress as far. (Depends on how self-driven she is.)

If she has never experienced fairly long term high stress, I'd recommend trying to create such a situation (with her knowledge and consent, of course) to find out. Some people thrive on it, some endure it, some fold or break under it.

If she has her heart set on a career as a violinist, she'll probably pick NEC. If that's one of many options, it might not be best.  The best school for violin is not necessarily the best school, and if she ends up being anything except a professional violinist, the better school overall will be the better bet.

If she is considering (or out and out wanting) to be a profession violinist (in an orchestra - you don't need credentials to play in small bands, just play well enough),  have her talk to some people doing that, and if possible sit and watch a rehearsal or three.  From what I've heard, playing in an orchestra is not for everybody (I wouldn't like it even slightly), and she should know what she'd be getting into.  It also pays the bills, but not much more. It's like most music. A few top talents rake in big bucks, most people make somewhere between a subsistence living and a modest one.