Sorry for the delay on this! I'd figured someone else might come answer your questions. ; )
Her game plan is built around getting close and then just overwhelming the opponent. Her BBB chain can cross to the other side with the third hit, which won't combo but does have to be blocked in the other direction. She gets a degree of invincibility with the startup on her ground C, which you can use to bait out a desperate attempt at a counterattack and then keep up the pressure by hitting again. You can also cancel the end of her ground A into B or C to continue adding pressure, too.
Her air C lets her get close from pretty much anywhere, while her air B does a tricky thing where it doesn't actually hit until after she lands, and the opponent has to block based on which side she lands on, not which side she started on. Also, her air A hits a very wide area, making it great for jumping over the opponent and hitting just after you cross to the other side, so the opponent has to block "toward" Valerie (known as a cross-up).
Basically, the idea behind Valerie is that she can be very oppressive when she gets in close, to the point where it's a relief for the defending player that the life bars are so short. ; )
To play against her, you generally want to find ways to keep her away, or find your own attacks that can win out against some of her offensive options. Grave, Rook, Midori,* Jaina, and maybe Geiger all have very good ground C moves to get her off them, but they tend to come with drawbacks, especially if you get predictable. You can also try throwing, since it happens fast enough to grab her out of the startup of some of her attacks, but that's also not a sure thing. Broadly speaking, your best hope is to simply avoid letting her get close.
*Midori's ground C actually beats most of Valerie's gameplan outright, making this a matchup where Midori generally has little interest in dragon mode. Valerie actually has to play very carefully against a decent Midori because that C parry is very good against basically everything in her repertoire.