Actually, I seem to recall in an interview with Frigga's actress before Thor 2 came out that Frigga is Thor's step-mother, not his natural mother, which puts hers and Odin's marriage a bit shorter than originally thought. If that's right, then they're probably using some comic canon that Odin married Freya first, who was part of the All-Mother. (The comics got weird. I still need to get that new Loki series in my collection.)