At a glance, this doesn't seem to be horrible piece at all. You came up with your own way to style Berry's hair to something resembling the crystal ponies, and added these colors to create a very unreal effect that makes crystal ponies... crystally.
If I were to spend a little bit of time looking at this though, this may have been executed more skillfully. A quick look at a screenshot I have of most of the mane 6 turned crystally tells me that not only does their coat change, but also their outlines. The effect applied on to the coat could have been also applied on to the lines. At the very least, the outline could have been a color a lot more similar to the coat. From experience, I've noticed that adding a larger variety of colors or adding more realism within a shape e.g. through shading makes more dissimilarly colored outlines (or outlines in general) less effective. I've tried detailing Rainbow Dash's hair while keeping her illogically blue outlines before. Results were ugly despite her unshaded vectors getting away with her illogically blue outlines without trouble.
I also don't really find the outline thicknesses hear the hoofs to be very convincing. While outlines in other areas like her hair taper off, it doesn't seem to be very convincing when they taper off near the ends of her hooves. Outlines tapering off works on her hair because I read the tapering outlines as if one shape is being merged into another shape. The legs however is one big shape, and the hooves where the outlines thin out aren't really suggesting anything to me. I dunno about how you feel about them, but that's just my reaction.
There's also an outline that appears out of place on the top of her rump.
Berry's proportions might (or might not?) have been better executed. In the dead center of this piece, you have a rather sizable butt. While this could probably work if Berry's gonna be wealthy enough to overfeed herself (eating grapes all day like a Roman dictator!) or just making her larger to convey a bit of age, I'm not much for these proportions. These proportions in general are much chubbier than show-style so I can probably infer that you were not aiming for show-style anyways. I dunno what other people feel about this though.
Other things I can see after thinking about this are hooves being different shapes. The Berry's lower back left leg appears mostly cylindrical but show-style ponies have all of their legs be slightly but still visibly larger in thickness at the hoof. You got that part down on the front legs though.
I think we should also be careful when drawing the back of the hoof with an acute angle. Berry's back right leg doesn't appear convincingly shaped if you ever looked at the shape of a hoof of an actual horse, or at least how the shape translated into the stylized ponies we end up having. Also, have you taken a moment and wondered what the back leg looks like behind the other back leg? If we are to keep the back legs the same size, instead of having a hoof that has a more acute angle on the back instead of the front, you'll have something that is opposite and thus does not convincingly resemble a hoof. However, the hooves on the front legs are much more convincing.
As for a suggestion for better way to draw that leg while keeping the position of the hoof the same, I'm thinking of make the lower leg more vertical, but have the upper leg stretch out. That will however make Berry look like she is walking, so if we were to have the back leg stretch out, will have a more convincing walk if we raise the her left leg up as if she's lifting that leg forward. You will have to angle that hoof so it definitely doesn't appear to be on the floor though.
If you also look at both ends on each hoof, they are differently angled if you were to draw imaginary lines from point to point. This doesn't make sense as I would expect the floor to be flat if there is no floor to be seen. What I end up seeing is a figure that doesn't appear balanced.
All in all, this definitely has its charm if it got into EQD (some of my pieces don't even make it there), but again, I think that the execution could be better to not just be good, but be even better.