Yes, it can take them a while to get it right and they're likely on the young side at that size. And, yes, she could be eating them because they're failed eggs-- what color are they when she eats them? also, what size tank?
Sev pair compatibility varies ime, it just does. There can be different pair histories and factors that come into play. Even previously successful pairs can have rocky spells where they bicker, can't get spawns right, then settle down again to be just fine. Or some will just have their ups and downs. But an ugly split can also happen, as mentioned. Bickering is one thing, a pair that really rejects each other can do some damage.
I agree with Ryan on mixing fish, but I can understand being on the side of the curve where you're happy to see spawning behavior and success means getting fry, I've been there before. The learning experience can be worthwhile, but there's hardly a combination that hasn't been tried already and I agree, the hobby doesn't need more mixed fish.