Due to her “smol” body, Remilia does not need to feast as much as a normal vampire. Whom generally do not need to eat as often as a normal person.
In addition Remilia has been show to eat sweets pretty often, usually with human blood baked into it, implying she can metabolize both.
What I will do is put some of my own blood in an ivy bag and get a dozen cakes, incite my self over to SDM. Tell Sakuya that I have an offering to Oujoi Sama. She lets me meet Remy where I bow down in worship of her beautiful body and tell her it will only get prettier with growth. I give her my manly blood bag and force feed her the cakes until they are all gone and she is looking a bit more womanly. I tel Sakyua to start pampering Remi more and even carry her around so she does not burn precious calories. I repeat on a bi-monthly basis until she doubles in size and squares in sexiness, while cubes in cuteness. I move in full time to take care of the soft vampire until she grows to become a big voluptuous lady full of me and my love, in a very literal sense.