Oh ffs. You have spectacularly missed the quite specific point of this thread. A number of widows have explained their experiences and feelings after traumatic loss. People have talked about older widows experiencing the same, where it appears that social exclusion occurs when you're no longer part of a couple, and other couples don't adjust to the new dynamic.
It leaves one feeling as though you're not enough, or you're a ticking time bomb, or any number of reasons in other people's heads that you're not privy to and you are left speculating as to why?
As I said previously the couples I am still close to knew me before I was with DP. One of those couples knew him separately as well - the circles we move in have many cross overs. Couples we only knew together as it were are the ones who have fallen away.
I'm certainly not a temptress of any sort at the moment. I have 6 inches of roots, I've started to go really grey. My face is puffy and I have loads of new lines. Two years of trauma are absolutely etched on my face right now.
Whether I'm considered a threat to anyone in the relationship department I don't know and I don't care but it's possible because people are complicated and messy and have insecurities. I've heard similar sentiments as the OP from another widow who was accused to her face of having designs on someone by their wife.
Thing is, for most, though possibly not all widows / widowers, their identity has changed - they are no longer part of the world before bereavement and trying to adjust to that is all consuming. People suddenly distancing themselves or treating you differently takes time to process.
DP and I were a bit "joined at the hip" socially. We both worked in separate places with a social vibe then went out and socialised together, out of choice. I've never had a big girly group of friends anyway. Sometimes we went out separately but mostly we didn't and it worked for us. Everyone is different. You don't consciously think "Oh I'd better cultivate friendships with individual peopke in case I end up widowed and all our couple friends don't want a third wheel playing gooseberry or sitting like a spectre at the feast at dinner parties".
That's not how life works. Life is organic, habits form, you have patterns of behaviour and it gives you security. When it changes dramatically and irrevocably it's devastating on so many levels. You can't know how things will be. There is no handbook for this shit no matter how much we think there should be.