Need friendship advice

I have this friend, we'll call her B, that I've been friends with for almost 20 years now. We met because we work together and when in with her I have a ton of fun. We talk about all kinds of things, and bond because we both have kids.

However, I was super sick a couple of weeks ago and didn't talk to her for like a week. After that, she messaged me if I was mad at her and I said no and explained that I was sick. Ever since then, things have been strained between us and I don't know why. I message her and I get one word responses. She's not messaging me. She went on vacation this week and didn't even tell me, and we ALWAYS tell each other when we have days off (we still work together).

The thing is that B can be kind of mean to me sometimes. I feel like I can't share anything important in my life with her because she'll just be. My oldest child is going through anxiety and depression pretty bad and when I tried to talk to her about it, she told me to stop listening to doctors and I needed to change his meds. And that I needed to figure it out for the sake of my child. Like ..it made me feel even more like shit. That's just an example, she's done this kind of thing multiple times.

So in half thinking of just letting the relationship fizzle out, but the problem is that we work together. We're on the same team and have to work with each other a lot. I hate that kind of situation (working with someone when there's tension) and will do anything to avoid it.

So what should I do? Message her to ask what's up? Let it fizzle out? If I do message her, any help in what to say would be great.

I feel like I just don't understand why there's tension between us. Did I do something bad? I have no idea!!

Thank you!