I have autism and so do some of my friends.
One of them was very much like this. He lived 'in the now' so, if he hadn't seen me for 2 days, he hadn't seen me for 'ages' and he questioned me (relentlessly) on whether we were still friends.
I found this overwhelming because, for me, a quick text exchange is as good as meeting up (and easier) whereas he needed constant social contact.
I found that having a set night of the week/fortnight/month worked for a bit until he started questioning why I couldn't see him more often and friends want to see each other and what was I doing those other nights that meant I couldn't see him. If I had a day off, why wouldn't I want to see him on days off? That's what friends do. He completely lacked the ability to understand I had my own wants and needs too. He completely disregarded that some of the times we didn't see each other was because he was busy! He just knew he hadn't seen me.
We bought a diary and coloured pens. Each of his commitments was colour coded to help him see when he was also busy and that he didn't have time to see me more often even when I was free. But eventually he accused me of using this to control and manipulate him because he could see there were days he was free when he still hadn't seen me and couldn't understand that on those days I was busy or just needed time to myself. Because he hated having time to himself.
Eventually, I just had to explain that I couldn't be friends with him anymore. It wasn't his fault but the stress and anxiety it was causing me was too much and the impact on my life was too great.
Autistic people might not naturally have the same ability to see the bigger picture but we can learn to operate within it. We can find strategies to manage the feelings so that they don't impact on others.
If she isn't able to do that then a low contact approach won't work. She expects/needs/wants hgh contact and will also be stressed and anxious by the situation. She won't be able to accept it. For a lot of autistic people, it's all or nothing. If you can't give her all, she will find nothing easier in the long term.