Oh, I really like this! Paradoxically you have these super dysfunctional elements, soir and angst but what predominates is the bliss of revenge (and good sexual alchemy, I guess!). Also! My headcanon for Astoria was never really set between brunette and blonde, but one of my preferences is basically Leighton Meester as Blair Waldorf in slightly curvier, so it's pretty much exactly what you describe, hehe.