Rosemarie posted on the cactus and succulent forum and I'm copying and pasting her comment below:
[Okay, somewhat difficult to say...I believe it is a type of Mammillaria. It looks to be dichotomous (branching-splitting into 2 heads). Mammillaria perbella & ,parkinsonii are known to do this (although they are not the only ones). They are both variable. I think M. perbella has darker pink blooms, so I'm leaning toward M. parkinsonii. This is a very large genus, so that's my best educated guess.]
I googled and found this photo for comparison:
