I hear ya. But breeding a normal cause it's all you have isn't the way to go. Bamboos are pretty affordable, it would make more sense to just buy one.
Plus there's a lot of risk in "loaner" animals when it comes to breeding. Just not worth it.
And not to knock the shop owner's girlfriend, but if she's considering breeding that animal to a normal she's cuckoo for Cocoa Puffs.