Japanease tend not to mention the idea directly. We also hestate to assert our opinion or ideas because if someone to talk with has the opposite idea, casual conversations trigger tention between them. Adding some words in the end of the sentence, we can avoid such a situation. Such a tenency makes foreigners get irritated because they might wonder if Japanese like or not. Also, adding "yo" or "dana" are used to withdraw an attention from others.

「会ったの」も「会ったのよ」も意味は同じです
ただ「～のよ」は、女性らしいイメージになる語尾です
「～だな」は男性も女性も使う語尾です
使い方によってイメージは多少変わりますが、文章自体の意味はかわりません

話し言葉の中で使われ、親しみを与えたり、時には相手に同意を求めたりする表現です。通常、目上の人には使わず、親しい友達や家族の間で使います。

「～のよ」「～よ」「～だわ」「～かしら？」は女言葉と呼ばれ、女性らしさが加わります。
「～だな」「～かな」「～だよね」は男も女も使います。

他にあるかな～？とりあえず思いついたもので。別に意味をあいまいにするために使うものではありませんよ！

it's difficult to explain it.you know we have very important grammatical rule it's called perticle.add to after verb and none and to variant meaning.だよ・だね・だ・だにall of those end form is same meaning.but sometime woman use [よ]会ったよ。会ったのよ。「な」too.this one make to turn down to mean.then this phrase mean I could say that I like French.opposite "I love French." I hope to help your understand it.