The only way I can think of without a DNA test is if she had a pretty good idea when she was ovulating and for whatever reason wasn't having sex with her husband during that timeframe. This makes me wonder if that is why the husband said she was 2 months pregnant but she only apparently got confirmation of the pregnancy 3 wks ago on Father's Day. Most women who are wanting to get pregnant would do the test after the first missed period.
If they weren't panicking.