There really isn't a way to get out of her locking you down during her oki game. You'll need to be able to block her mixups and find openings to escape or press buttons to get out (which I don't really recommend, with the speed of SLab's normals). Obviously, there's the option of using DP or counter assault/dead angle, but they're both risky and use up resources of yours. Focus on the Chie's pressure and mixup so you can find an opportunity to get out (punishing unsafe moves, using instant block to create larger gaps in their pressure, etc).
Basically, you're gonna need to learn how to be on the defensive. Since SLab lacks moves with decent startup speed and a furious action that's a bit easier to bait than others, you're going to need to pay attention to your opponent and how they pressure you.