ChilledBee
I feel the same about my marriage and, like you, this is deliberate. I would be fine, emotionally and financially, if we split. I have made it that way, because I wouldn't like to be dependent on anyone other than myself for emotional or financial security.
BUT, what I would find very distressing, would be if DH cheated and I as suspicious, but didn't find out for a very long time, until HE had put all his ducks in a row, was truly in love with someone else and was leaving. It's the bit between being happily married and being alone.
For that bit, I would rather minimise the pain, by having a good understanding of where we were. And that would include mentioning if I thought DH was embarking on a friendship with someone that was bordering on inappropriate.
What inappropriate means will be different depending on the couple. For the OP, because the DH doesn't have many friends and has never had a woman friend and because OP believes he's enjoying the female attention and the woman in question is apparently quite disinterested in the OP; this is inappropriate. For other couples it won't be. My DH runs with women at work. Of course that's fine. They work with him and probably have minimal interest in me. That is also fine.
But this has always been the state of things.
It's changes in behaviour are always a bit of an alarm bell. So, maybe if my DH stopped running with everyone but a certain woman, she started calling and texting him at all hours of the day and night, they started meeting up alone together in the evenings and weekends. All of those things could have innocent explanations, but I would at least need to discuss it with DH and he would be the same with me.
For the op, the new friendship her dh has, along with him saying, "you're ruining this for us", would worry me a bit too. And it wouldn't be because I fear being alone in general. It would be that bit in between I wouldn't like.
Anyway, arguably, the DH here should be more worried about finances than the OP, as he is a SAHD isn't he, so has no income I guess.