Like others have said, I would recommend communication - asking (gently) why not. But please respect her if she can't/won't talk about it.
Not every lass likes/loves it, some have bad history, and some have certain aversions to it for various reasons. But you will never know unless you ask and give her the opportunity to tell you. Why not start off by saying why you would like to, and then ask her how she feels about that, before asking her why not? Try not to make it "Why won't you let me", but rather, "I would like to share this with you because..."
Are you able to finger her? Can you get some pleasure from tasting your fingers instead of direct mouth-to-pussy? Is there not some compromise you could come up with depending on how your conversation goes?
Good luck!
Ha ha, swollen! Want some coffee? I'm just going to get some!
Thank you for the replies! I did notice just now when I pasted from Word (an ancient version) into the Stories Space submission form, nowt came up, but it was just as it should be. But it was a story, rather than a poem, and I can't remember if I had to re-jig the poem or not.
So next time on Lush (if there is one!), I will try an experiment...