According to the user guide, the manufacturer recommends a 10M ohm impedance preamp. That's a very high impedance, which might even exceed the guitar/"instrument level" input on some mixers (contrast with "line level" and "microphone level").
The short answer is that unless your mixer has a matching high-Z input, then the violin is going to sound thin in a manner very similar to your experiences with electrical guitars. It'll work in the sense that you can get a signal from the violin pickup, but you probably won't like the result. Updated: A regular DI unit might not have a high enough impedance, since electric guitar pickups are in the 20K to 40K range. For maximum flexibility, your friend should consider getting a DI unit with an input impedance that matches the pickup.
Here's a good overview of impedance in relation to sound recording. According to this, the Fishman V-200 is a high-Z source. It's okay to connect a low-Z source to a high-Z input, but the opposite has consequences:
If you connect a low-Z source to a high-Z load, there is no distortion or frequency-response change caused by this connection. But if you connect a high-Z source to a low-Z load, you might get distortion or altered response. For example, suppose you connect an electric bass guitar (a high-Z device) into an XLR-type mic input (a low-Z load). The low frequencies in the signal will roll off, so the bass will sound thin.
We want the bass guitar to be loaded by a high impedance, and we want the mic input to be fed by a low-impedance signal. A direct box or impedance-matching adapter does this.
I don't have any experience with the Fishman V-200 pickup, but trying to plug in electric guitars and basses into low-Z inputs is a pretty common problem that a lot of musicians have run into at some point. Without the Internet, or some knowledge of electrical engineering, the result can be pretty baffling :-)