I subscribe to love theory.
Friend isn't polyamorous and doesn't sound from the original post like she returns the feelings. So there's no 2 way romance thing there between you.
There's no commitment built there at this time either. To me it seems like the only other corner left is to park it at this time is the "infatuation" corner.
And that's a crush to me. I didn't mean it in a mean or minimizing way. There's nothing wrong with enjoying a crush. For years even! They are awesome.
But if that's as far as this one can go, then that's as far as this one can go. Limit reached.
I've resigned myself to accepting that we will just be friends and I truly do want my friend to find that person she is looking for...and I know it is NOT me.
Sounds reasonable then. If it isn't a runner it isn't a runner. Could keep enjoying the crush to yourself, and focus on being her friend.
Hang in there!