Difficulty letting go/not thinking of narc ex-friend

Been trying to let her go for almost seven years. Known her for about 25 years.

She texts from time to time and I have slipped and texted her.

Other than No Contact, how do you LET GO?

My birthday is in a few months. I know she will text me on my b-day if not sooner.

I am working on the NC thing, other than that how do you stop obsessing about your old crowd?