thumb-rings and long fingernails

Not quite sure if the problem is with the ring? Is the problem that the long nail is hit by the string, or is it that the long nail interferes with the index finger when it locks the thumb?

When my own thumbnail starts getting to long (I'm lazy) I feel it interferes with my index finger covering it. Adam Swobodas book (sorry don't have it here, lent it to somone, can't quote) speakes about different placement of index finger in relation to thumb. The index finger close to the tip of the thumb is obviously not good in this case, but maybe placing the index finger near the root of the thumbnail might help?

I can't quite see how a shorter lip on the ring will help, maybe rather a thicker lip might help the string clear the long thumbnail?

The actual problem is me not knowing how to cope this conflict of nail-fashion with thumb-archery. I never had long fingernails. Even in my guitar-decades I preferred a plectrum and short nails.
Her difficulties are finding a proper lock, string-clearance and - last but not least - a reasonable amount of fear of a very likingly hurting string-slap against the thumb-nail.
So I thought about a lock on the bowstring with a straighter thumb. Therefore a shorter lip could force her to put the ring (instead of the thumb-tip) against her curled-in middle-finger to achieve the lock.
I think a long ring would be good if these nails were in somewhat the same length... but they change regularly making this even more unpredictable. I am therefore hoping to use the short ring as a reminder for her to open her lock quickly and to leave the thumb straightish. A curled in lock like 63 would do her no good.
Additionally she can't curl her middle- to little-finger too far... because of (again) long nails there, too. So she has to go for a straighter thumb anyway to reach the second joint of the middle-finger for the lock.
To avoid any interference of the index-finger the lock will be in 90° angle to the bow-string. (at least that was easy to solve...)

Since you mentioned the index-finger locking the thumb, I just want to mention that me and lots of my thumb-archery-friends avoid this. We like the middle-eastern manuals and all of them instruct not to tense the index-finger. And we get along well without index-finger-locking, even with +80#. Just to let you know where the ideas of thumb-to-middle-finger-lock come from.

I can see the problem(s) I don't know if we are talking past each other, but you do cover the thumb with the index finger? I don't mean clenching hard. But maybe the short ring could help. I really don't know.
Other than what I said above I don't have other suggestions than maybe to start with a very weak bow to lessen the fear of the string hitting the thumbnail, and then work up as it gets more comfortable.
I remember when I started with the thumbring it felt awkward in the beginning

I don't think we are talking past each other. I was adding details about my understanding of the lock to increase the chance of avoiding this. And yes the thumb will be covered with the index-finger, but it has "a merely decorational function". So I guess the point of a lightly and relaxed covering of the thumb is just more stretched in my way of describing the lock, and that is all.

So a thicker lip could help, and some adjustments in length. I think it's best if I just ask her what she prefers. Longer or shorter could help. The suggestion to a weak bow is a good one as well and as always. She is currently shooting my 20lbs practice-bow and I think this is just fine for learning the motions as well as for overcoming hesitations and awkwardness with the lock.

Thank you for your view on this topic. :)