Anne, it looks like P. obovata to me, just not alba. I grew alba for a long time, raised from seed from my parents' plants. The flowers look the right shape, and the 'naughty bits' look right. I recall the leaves of P. obovata alba being a bit more greyish, but might might just have been alba. The pink form could be greener in the leaf. Having said all that, if the parent plant was grown near other peonies, like molokosowitzchii (hope I've spelled that right without the aid of a ref. book!), it could have crossed!
