Yes, if you're very close friends, then let her know how you feel in a peaceful, caring way. She might be going through many feelings, but on the surface, she seems fine. She might open up if you talk to her. Wishing you the best.
I have a very good friend but since I had a baby I barely managed to keep up with our conversations. We also live in different countries. She moved back home and trying to rebuild a life there. It takes us sometimes a few days to end a conversation because life gets busy. When I remember we call each other and spend at least 2h on the phone but that is maybe every 2months or so. When we talk I know there is trust and real friendship between us but I also know we give each other the space to live our lives. I would love to be closer or speak more often but I also know time is not always in our favour.
If you guys are really friends I would tell her my feelings of her being distant. If she is genuine she will have an open conversation with you. I hope it works out . You guys have been friends for years.