Sorry, but assessing the performance of a base layer when it's three sizes too big is totally pointless. She's wearing a large and should be wearing a small. It's not gonna wick sweat away from her when it's hardly even touching her skin!
When there's a 1% discrepancy in the materials it's not going to be a huge difference. Granted the fit and finish will be better on the Rapha garment but I can't see that being worth the price difference.
Sorry, but assessing the performance of a base layer when it's three sizes too big is totally pointless. She's wearing a large and should be wearing a small. It's not gonna wick sweat away from her when it's hardly even touching her skin!