Is this a Mammillaria sempervivi or something else?

I've been asked to try to ID the plant in the photo below. I am struggling, so I thought I'd ask here and hope that it strikes a chord with someone. It is quite an old plant, possibly grown from De Herdt seed, and is named as Mammillaria sempervivi. However the definitely pink flowers have made me wonder, though I know that away from the area around Venados in Hidalgo, there are plants with cream-pink flowers which tend to offset, and have been called M. sempervivi. My thoughts obviously go towards those, but also to M. pseudocrucigera. Its the pinkness of the flowers that worries me. Without any habitat data it is difficult, but I would welcome any advice on it.