Well, that is certainly a peculiar question Muro.
From the vampire perspective, the blood elemental is a very desirable thing, it is a walking resevoir of blood, or vitae (to use VtM terminology) that could conceivably regenerate itself by various means. Any capable vampire would want such a beast under its thrall.
From the elemental perspective, the Vampire would be it's anathema as being a blood elemental it doesnt even have a basic element of humanity to foil against the vampire's unnatural hunger. The elemental would run the risk of being devoured, being made of blood, and since the vampire itself is a thief of blood it is concievable that the blood elemental would not be able to use its powers, whatever they might be, against said vampire