She often shies away when one extends a hand towards her

Here's my non-scientific method to 'cure' this 'syndrome'. Pick her up at odd times, almost unexpectedly (it's good before a meal when she's hungry), and hold her to your face/the crook of your neck for about 20 seconds. You can even go through the moves of 'scenting' her with your cheeks. Then, gentle place her in a safe place or in front of her food bowl. This has worked for me twice in the past. The cats in question usually responded within 10 days and were better within 1 month.