Does anyone here know anything more about 'Bellard'. HMF lists both an alba and a gallica by this name, with the same date, before 1857. I do not suggest that the two entries should be merged without some form of proof that the two roses are one and the same.

Vintage Gardens Book of Roses has an entry for a Gallica "BELLARD.......unknown [breeder],c.1857" The description sounds very like the alba pictured at the Trevor White nursery in England. VGBoR, 2006 ed., p. 11.
"translucent shade of pink"

MR10 has an entry for "BELLARD A. (OGR), Prior to 1857"

VG received their plant from the San Jose Heritage Rose Garden, which doesn't take us much further.

The Old Rose Adventurer (Dickerson, Brent, Timber Press, 1999), p.34 lists a 'Bellard' under Gallicas, with synonyms 'Bellart', 'Bellotte'....."color, bright pink, with a light pink exterior". That description could maybe fit the rose pictured in the Trevor White catalogue supposing the picture had been taken after the flower had faded some.

https://www.trevorwhiteroses.co.uk/product-category/alba-roses The rose pictured at Trevor White is clearly not identical to Great Maiden's Blush, also pictured in the same array.