<Snipped quote by Vordak>
For the non-solid parts, I would say as strong as, let's say, Goku's Kaioken x1. the parts that are solid, like on Alexis' skin, I would say something akin to the durability of solid rock, maybe slightly more than that.
Now, i know this may sound ridiculous, but then the dagger's tip would just slip past, ricocheting away from her arm and meeting with Alexis' forehead instead. Since the strike would be coming from shoulder level to the face, Vos'stoorge's wrist would already be turned upwards, preventing it from slipping downwards, and the hardness of the shell would just prevent the dagger from getting stuck in her arm.
You even specified in your post that Alexis intended to block the strike, not push it aside, so you've pretty much written yourself into a corner with that hasty of a post.