Are we still friends?

I’ve learned so much from SCS so far, as always, thank you!
I’m now in the very best committed relationship I have ever had in my life and it’s partly due for sure to things I’ve learned here. I have an amazing partner now and I’ve become an amazing partner too 😃

My question today is regarding a long time friendship that I’ve had.
For several years, my friend and I would talk frequently on the phone and were a source of support for one another.
I feel like the friendship was pretty balanced and very healthy overall. We helped each other through some of the toughest times in our lives.
Over the last several months however, my friend seems to have “gone dark” on me for the most part.
She seldom calls or texts me and when I reach out, it takes days before I hear back from her. Actually, it’s now been over a month since I left my latest voice mail on her phone.
I don’t know why this is. She’s the type of person that nurtures friendships, when she’s deemed them important (she actually shared this with me several years ago). Seems I have now fallen off of that list.
Or, she’s gone into “turtle” mode which she has done in the past if things aren’t going well for her but that does not seem to be the case based on our latest interactions, she just says she’s super busy.
I could coach myself through the situation and accept it for what it is even though I really miss my friend. I considered her to be my closest friend up until the last several months.
Should I simply do that (coach myself) and just take things as they are, or should I openly reach out to her and have a heart to heart about it?
I am torn.