Anxious Attachment and Codependency: Switching Targets

My anxious attachment has latched onto my s/o. Right now, I've acknowledged that a close friend of mine may not be my best friend. I've realized that I can choose what I do with the friendship, and I've felt better lately because I haven't been obsessively overthinking about her. I feel better, but sad too, because it feels like we may be drifting apart after so long. Anyways, my anxious attachment and codependency are still there, and it seems they need someone to latch onto. Whoever feels like my true #1 best friend is always the target. Now, that's my s/o. It just clicked. I feel detached from my friend and anxiously attached to my s/o. It's like they just switched so drastically after years, and it feels really weird. It feels so sudden and scary. And also, I don't want it to be this way with my s/o, or anyone. I really don't want it to ruin things and I'm scared of that.