Hi Normandie,
maybe just another instance of talking past each other here

and please don't mistake my explaining for being aggro/debative. I just want to bring over what I think.
Soooo...
Yes, most unbonded men (including Freeman I agree) would have a one night stand if given the chance.
Yes, sex can be a great calming/uplifting thing.
Yes, some times sex in the face of death to celebrate life can happen easily (BUT this psychologic mechanism commonly means a death threat on both parties, it's known e.g. for people during war before an attack or during ceasefire, and we do not have this situation here regarding Alec)
Seeking out a woman for anonymous one-time sex, already knowing that the sole reason you do that is to plug up or forget a feeling of sorrow is exploiting the woman. It's not about having fun together. It's not even about sex.
Incidentally half of all women having a one night stand have negative feelings the next day, the majority due to feeling "used" (
reference). Things are definitely not as positive about this little sexual happenstance as media have made us believe.
Any halfway intelligent and sensitive woman would cotton on rather fast to why Alec seeks her out in this particular case, and yes she would feel used, and my perception of Alec is that he would know it too. He never was portrayed as a psychologically inept klutz by Sewell (the joke among them was that Straker is). I don't think he would do it. Things might be different with a longtime fuck-buddy whom he visits for a cuddle, but even then - see below.
Lastly, death of a close relative or beloved person usually turns one's libido OFF rather completely. Which is why I think that the question doesn't even pose itself.
What I could imagine is Freeman going to a good, "old (female) friend" and get a cuddle - some food foisted on him, a whiskey or two, being comforted while he talks about Straker, tucked into bed and held. No sex. That would be what psychologically makes excellent sense. A ONS doesn't.
As to women being "perfectly happy to seize the moment", see that research and there are more on the same topic giving similar data.
Personally I don't think the picture portrayed by movies, TV or media, that women do it and love it for the same reason as males is correct. I think many women will agree with ulterior motives, like e.g. securing a longterm relationship, or because they feel pressured into agreeing. Quite a few may have been caught out in a situation where they feel a "no" is no more an option (which ends with them feeling quite a bit like date-raped women, only they blame themselves for it even more so).
My personal impression is that it's the married/bonded women who have a quickie on the side with an attractive, willing man they chance upon who are those most likely to enjoy a ONS without misgivings.
In any which case - it is an interesting topic. Especially if you want to have people act realistically in what you write.
And again - YMMV.