The Core Rules say nothing about this that I can find.
I seem to run into this situation a lot but I don't think I can really clarify: Can I prepare the same spell multiple times?
The core rules indeed don't explain a lot, but you could refer to the game BFRPG is "cloning", Basic D&D, that says on page B15 :
A spell caster may, however, memorize the same spell twice if he or she is of a high enough experience level to do so. If so, only one is "erased" when the spell is cast; the other remains and may be used later.