My grandma used to be just like this.
I found that telling her not to worry makes things significantly worse.
In that vein, I would suggest that you don't explicitly talk to her about stopping to obsess over you. It is likely not going to reduce her stress and anxiety around your visits, but increase it.
I also found that limiting my visits made things even worse, and that it caused her great emotional distress and made her think she's failing me and I'm distancing because of that. I strongly recommend against doing that. I cannot stress enough how bad of an idea this was for me. I thought at the time I was doing my gran a favor because she wasn't well. Instead, I contributed to her depression by making her think I wanted nothing to do with her.
What I found to work is to accept that she'll obsess over you and to steer that in a direction that is helpful to you and doesn't create a lot of stress for her.
When you plan your visits, ask for something simple that you enjoy, like your favorite dish or activity. This has several advantages:
- It will make her feel needed, which is often the motivation behind this behavior
- It will remove the stress of not knowing if she's doing the right thing (this was the biggest stressor for my grandma back then, she was constantly afraid I wouldn't like what she thought up)
- It will make visits easier on you