Welcome to staph_aureusxx’s page.
Contributor score: 3
I think it's also important to realize that their veganism is the giveaway. Vitamin C is in fruits and vegetables and wouldn't be lacking in her diet. Vitamin D3 is mostly found in milk supplemented with Vitamin D, though it can be found in smaller amounts in plants as well.
Additionally, if you want to get reeeeally picky about collagen synthesis as an answer choice (cuz I was debating picking that one as well), a vitamin C deficiency causes an issue with collagen cross-linking rather than "synthesis." I know it is nit-picky, but the question says the vitamin deficiency DIRECTLY affects the process.
I nearly went with something to do with collagen synthesis, but what changed my mind was that it said that they did not give the patient ANY dairy products.