... is to not block her. If she's still on and sees you, she will know you have moved on. If she's not on or active, it's a moot point. If she reaches out, decide if you want to pony up for a bonus BCD and let her know if you are interested.
Like PaPa Sweet, I also never promise exclusivity, and I always assume she is seeing other SD's. However, I generally let her assume I am not seeing anyone else "right now." Which is always true since I don't date two SB's on the same day. Semantics? Hell yeah it is.
The lesson I suggest for you is that SA is not, and will (probably) never be, a place to find your soulmate. As I've said before, all arrangements end. The proof? When you two decided to move from SD/SB to BF/GF it fizzled. I propose that if you had continued to give your "GF" allowance, the fizzle would have stayed a sizzle.
Not saying she lied or misrepresented her intentions deliberately. But she signed up for SA for the funds. Finding a guy she actually liked, admired, respected, etc., was the gift with purchase (GWP). But like the GWP every woman has ever obtained at Macy's or Nordstrom's, if the $200 bottle of perfume wasn't in that stylish Gucci tote bag, she would not have made the buy.
Life is good
The Cat