I find sex scene are almost always a rather odd De-tore from the story itself, it doesn't really add anything in or move the plot forward. in some cases they can be appropriate, but unless you've been building to this point, it's just kind of a pointless narrative. That said, no you are never to old for a sex scene. just use your imagination.
I don't care for sex scenes myself. I don't write them if I don't have to, and they're really not that hard to avoid in SF/H/F genres.
I have written them though. In one book in particular, I felt it was best to go ahead and get into it just a little. Just enough to evoke a certain feeling from the reader. Just enough to create the emotion I was going for in the scene. It was important for the book, and had to be in there.
Like anything else, such as violence or gore, you put in what gives you the desired effect. If glossing over it is fine, you can do that. If you have to get a little deeper into the weeds, so to speak, well, you just gotta roll up your sleeves and wade in.
I just don't get why some people, mostly critics, seem to think that only literary books are 'real' books, and that commercial fiction success isn't as good as literary success.
I've heard writers say it sometimes too. It's sad. A good book is a good book.
I think that's the case. Many genres get stereotyped into categories that are nothing more than "guilty pleasures", romance and erotic fiction probably the most of all. I've seen it with other genres as well, especially the more "commercial" fiction.
Pretty much every genre out there except for literary fiction gets the stigma of being "not serious work" or "written for money". Literary fiction has the stereotype of being snobbish and pretentious, and with some merit. People speak about it as though it's the only real thing with written work. It's written because it's original, or avant guarde, or from the mind of some kind of defiant hipster genius. It's put up on a pedestal and worshiped like some holy grail of the literary world.
Truth is, most of the famous classics wrote their stuff as just a great story, in an age where their work was considered pulp fiction. We've just put their stuff up on that pedestal and labeled it literary long enough for it to have stuck.
This seems like a case of her needing to complete her bucket list, but it's a list which may have precipitated from that thought that her stuff was just pulp fiction for the masses and wasn't "good enough" to stand by literary fiction as an equal. If so, that's sad, for it just perpetuates that mindset.