I'd call to ask. Did they actually say they do no meat/milk combos? That's typically a stricter Jewish thing, so not all Messianics do the meat/milk prohibition. If you know that they absolutely do separate the two, then I'd just ask her. Also, if they are strict enough to separate meat and dairy, then you'll need to definitely watch your ingredients for kosher certification. The burritos might still have milk in the tortillas. Usually, whatever kosher certification there is will have a "D" next to the company's kosher logo if there is dairy (or a dairy derivitive) in the food. If the kosher logo has a "P" or the word "parve" (sometimes also spelled "pareve"), then there is neither dairy nor meat (or any derivitive animal products) in that item. If the kosher symbol has no D, no P/parve/pareve, then it still has some sort of kosher meat (or derived from meat) ingredients.
So I'd definitely call them to ask. I'm sure they appreciate the attention to detail.