Mine is maxed some time now, she also received a few emblems. I like her high stats, the special is not spectacular but still meaningful. I have not yet used her in defense, in attacks she is good and I personally like her more than Vela due to the higher upfront damage and the better stats. For raids, when attacking with blues I often use other blue heroes ahead of her (have a solid blue five star bench). In war, she comes out to play. As usual, all depends on your options, she is an above average blue in my opinion.
I’ve been using her with Vela, Krampus, and Costume Kiril and a sniper. Vela is +18 and she is +6. Krampus and Kiril both fire in 9 tiles. If they all charge at the same time I get about 650 direct damage total(350ish from Crystalis and 300ish from Vela) on each enemy and another 123 dot each turn. The bad guys are mostly all dead by time the DOT ends.