The official Skullgirls account has announced that owners of Skullgirls 2nd Encore will soon be able to play as Black Dahlia this week. Nintendo Switch owners can get access to Black Dahlia on Friday, 31st March, which is thankfully this week. Skullgirls is available right now on the Nintendo eShop and Black Dahlia will be available as paid downloadable content with the pricing set at £8.99.
Black Dahlia comes to Skull Girls 2nd Encore this week

I forget if these new DLC characters are free or paid content
The last 2 characters were $10 each. So I’m assuming the remaining 2 are also going to be $10 each as well.
You can buy them separately for I think $10 each, but the season pass is $35 meaning you get one character half off, plus some extras (Umbrella and Black Dahlia have alternate voice packs, every character gets an additional color palette, etc.).