Your learning curve is going to be hellish. The C1000 is NOT flat, far from it - it's just that you picked a microphone well known for being a right PITA! It's the microphone of choice for many schools and colleges, and is just a pretty unforgiving, hard, brittle, revealing microphone. It can sound good - BUT, and it's a big but, it's has the unpleasant characteristic of being suitable for some sources and terrible on others. I found it quite nice on a weak cello - just pure luck the two were a decent match.
However, the first thing you need to do before wasting money is listen seriously to the tone of the instrument in your recording room. Block up one ear - and ear plug, or even a jam in your ear bud type headphone and leave unplugged. Now use your ear like a microphone. Pick the spot you would have put a mic and have a listen to your girlfriend playing. Listen for the tone of the two lowest strings, and listen for the tone when she plays on the highest string nearer the bridge. What does it sound like? Hard, mellow, strident, beautiful? Chances are that the room will play a huge part in the sound you hear, and see if you can find a location where it sounds the closest to how you want it to sound. Frankly, it's no use whatsoever asking her. She will have spent her learning life on the instrument listing to it's close in perspective, an will use that as her yardstick for comparison. This isn't what everyone else hears. Once you have found the best position, then that's where the mic goes. If your instrument is strong at the bottom end and you know you will need less of this and more of the HF for detail, then a small diaphragm condenser could be the nice choice - and not even a hugely expensive one. If on the other hand it's weaker at the bottom, then a large diaphragm type could redress the balance - this all before you even touch the eq. If you record in a gorgeous sounding room, then a more distant mic position will introduce room sound. If the room is square with parallel walls and ceilings, then it will probably not be good for recording in unless you treat it properly, and moving the mic closer is the only option. If you do this, it becomes very dry, so a decent artificial reverb is your saviour.
This leads on to the recording software. It will do as a basic DAW - but it's not the best in the world, or really even close. It lets you record with no problems as the key feature is the quality. It's a new piece of probably ok software, but most people use cubase, logic, adobe audition, the freebie audacity or a few others. I don't know anyone yet who uses the persons - don't mean it's rubbish, but I suspect the add ons are where they make their money.
Mic choice wise - once you know your weak area where the instrument doesn't shine, you buy a mic known to flatter that area. Not all instruments record well at all - some expensive ones are truly dire, but in a church or concert hall use their sharpness or cutting sound to advantage. These ones record horribly in my experience. You also have player defects to consider. The sniffers, the ones who make odd noises and the worst, the ones who seem to create so much bow noise you find it impossible to control. Some just seem to have a permanent squeak, others play with gusto and you can hear their fingers hammering on the fingerboard! Some instruments are also more directional, so if they are an animated player, they change the mic position to the instrument by far too much impacting on the levels - and a fluctuating level is almost impossible to repair or disguise.
The Rode could be good, but possibly not - we really cannot tell you. Hence why we asked to hear what you recorded, we're more interested in the sound captured by a mic we know well.
You also need to get out of thinking about money. I know you have a budget, but in music, if the mic to do your job is 650, and the 590 is not as good, you will kick yourself for ever. On top of this - what if you then have to record something else your 590 is less good at but the 650 one would have managed? For your entire life you will be faced with this choice, and I have too many mics that are good for one thing, and very few good for everything. If I had bought just two good on everything mics, and not bought the rest, I'd now be richer!
Seriously though - we do realise what you mean about the budget - but I suspect you will not find it a problem to get something nicer sounding (note: not better - just different!)
Also worth noting that you might want to persevere with the C1000 and experiment. I, and loads of people really despise the damn things, but some people have got good results with them - on certain sound sources. In my head I can hear your recording already.
EDIT - sorry for duplication, but this took ages to type!
EDIT EDIT - just played the recording and yes, that's a C1000.
I'll leave others to comment on possible alternatives, but you also have a couple of playing issues that will be tricky to manage.
She does have a percussive fingering technique, you can hear this plainly, but she's also playing an instrument that is very lively, damping wise, and too many string changes leave the old one ringing. Some players cover this with their left hand fingering technique. The strings she uses also have damping built in to the wound ones - the trouble is that lively strings respond really well to quick bowing, and more damped strings resist the startup of the bow, but these ones don't ring out so much. From a distance, as an audience hears the instrument that sound you recorded isn't heard - but close in it is. I suspect she will not, at her standard, be able to change her technique - she's too good, so only a more distant mic position will work with ANY mic. This means a decent room. All tricky stuff.
As for compression - if you can hear it, it's too much. Compression is not a viable technique for this type of music - in fact, squeezing the last bit of dynamics out of it is normally the quest. Violins sound weird with compression.