How to explain to neurotypical people that socialising can be difficult and that not all social situations are equal?

Hi, I feel utterly distraught and overwhelmed at the moment. I started a PhD recently and it's been a lot of new things and I have been feeling quite overwhelmed. I got some feedback from my supervisor that I should try to join in more socially and particularly join for lunch. I joined twice in the past but I find eating socially very difficult and find group situations difficult too so I had decided that it is just not a good idea to join for lunch at this point (I have had a lot of issues around food anyways, plus I have IBS, made worse by stress. I've been doing much better in terms of eating and food diversity, but I just need to be relaxed and alone for this at the moment. And unstructured group situations are really hard). At first I thought I could somehow meet my supervisor's request to join in more and join for lunch occasionally but I just feel so overwhelmed and already way over capacity and I can't do it right now. Not without severely impacting my ability to function and work. I also find the office environment almost impossible to work in as it is busy and noisy and I have only ever been able to properly focus on desk work from home. I now feel so guilty to do some work from home and kept trying to do more in the office but it just resulted in me getting nothing done and having a panic attack. Technically this could work very well, I live close to the lab so it's not really a problem for me to go home if I have longer stretches of desk work. A lot of the time I am doing experiments in which case I of course have to be in the lab. Though even for that I have had issues recently and sometimes I choose to work late or on weekends as it is quiet then and I can focus much better. After my supervisor's feedback about trying to be more social I have felt so inadequate. I have been socialising one on one and I have no problems at all talking to people at conferences about science. This is fine as it is my special interest and it's predictable. But somehow people seem to assume that because I currently cannot go have lunch with people or focus in a busy office that means that I am utterly incapable of all social interactions, including those essential for my work (like talking to collegues to share ideas or attending conferences and meeting people there). I spent most of the weekend crying because I feel so inadequate. I've worked in quite a few labs before and this has not come up as an issue and I made some very good and lasting friendships. But now I just feel so defective and broken. 

And I just talked to one of my best friends about it and her response was that my supervisor's request is so reasonable and I need to work more on myself and push myself to join in and get used to the office. This makes me doubt myself even more. though I know from experience that what I need more than anything is some down time on MY OWN. I miss lockdown terribly- (apart from the fact that covid of course was not good at all), I really flourished during that time. My friend just now even said that she thinks I should find a different career (where I do not have to interact much with people) and not stay in academia- this makes me feel even worse. I am so confused. Deep down I know that I can be good at this and I just need to stand up for who I am and work in the way that works for me (which is what I did in the past). But I feel crippled by guilt and feelings of defectiveness so I keep trying to work in a way that doesn't work for me. 

How do you explain to people that for an autistic person socialising is not something that gives energy and that not all social situations are equal? Ie Science discussion with a stranger that I do not know is perfectly fine but lunch with my group is too much? 

I feel like such a failure and completely misunderstood- but I don't think I can change who I am?