Just need to get it off my chest

As an fellow adult, please help me understand this.

My best friend and I have been friends for about 7 years. We used to spend time together all the time, until she started dating her S/O. Now, I realize that in the beginning, this is going to slow down because she has someone new in her life.

Now, 5 years later... I feel like I'm her last resort. She complains that she doesn't have any friends besides me, and I partly want to tell her what I think might be causing that, but i dont want to hurt her feelings.

She's literally only available to text/talk/hang out if her S/O isn't around. If her SO is at work or with friends, she constantly wants to hang out. But the moment her SO cancels and decides to stay home, she immediately cancels as well.

In the last two weeks she's canceled on me four or five times because her SO is all the sudden available and home.

I get it- to an extent. I love spending time with my husband. But i dont have to be with him every single second he's available. I make time for my friends, I call and text them, I don't wait for him to go to work or hang out with someone for me to make time for people I love.

Do you have friends like this? ARE YOU THAT FRIEND? Please help me to understand. I feel like I'm losing my patience with her on this.

I wanted to edit to say:

They're like most traditional couples. Together every day after work and every weekend. Just like my husband and I. With the occasional night where her S/O has to work later than her by an hour or so.

I love spending time with my husband too. It's super important. I don't neglect him but I do spend time with people other than him on occasions. I mean, not often lol so I guess when I finally make plans to, it's highly annoying when they're cancelled last minute for literally no reason other than her S/O is suddenly not hanging out with a friend after all.