The use of "見かける" doesn't seem to have anything to do with whether you know it or not. I found some examples and we can see "見かける" is almost equivalent to "come across" in English. 野山でよく見かける花 Flowers we often see(come across) on wild mountains 良く海辺で見かける石 the stones we often see(come across) on beach 田舎で見かける建物 The building which is often seen(come across) on rural area インターネットでよく見かける用語　 Words often appear on internet 最近Twitterなどでみかける言葉 Words often emerge on Twitter recently 英語でよく見かける101とは？ We often see(come across) 101 while reading English. What does it mean? ネットで見かける「オワコン」とは？ We often come across オワコン on the internet, what does it mean?

Привет Eлена! Both sentences are correct. This expression does not limit what you notice or see. If there were a case, "知り合う". You can never "get to know" with somebody you already know.