We had a look in different shops but I couldn't decide; however, there were three that struck my fancy: one from Karstadt by "Paradies" (which is, I think, the same brand of pillow I now have), one from a shops specialising in health care which had a neck depression and firm spots on the sides for when you lie on your side (and even small depressions for your ears!) and which you buy in a size to fit you as exactly as possible so that your neck and spine are supported, and one which "reacts to your body warmth" and moulds itself to the right shape, and which you can return within 30 days if you're not satisfied -- unusual for something that comes into such close contact with your body.
Stella was more for one advertised as being good for people sleeping on their stomachs since, she says, she doesn't spend a lot of time sleeping on her side or back.
Unfortunately, the pillows I looked at were all in the €80-85 range, which was too expensive for the money Stella had saved up. She says she'll have another look on Monday when the end-of-winter sale starts to see whether they'll reduce the price for some of the pillows (it doesn't hurt to look). Otherwise we'll just have to wait a little longer.