The distinction is in how the information was presented and there is a difference (let us ignore the ages and assume i met the younger one then seeing as I met

The distinction is in how the information was presented and there is a difference (let us ignore the ages and assume i met the younger one then seeing as I met one girl my space is {(F,F), (F,M)} vs {(F,F), (F,M), (M,F)} for at least one girl while accounting for age). For the second age does not matter so much as who is older and accounting for all combinations is why I present it that way. The distinction is tricky but problems like these are often covered in the conditional probabilities section of most probability theory texts.