The audio sounds to me like "כן, אני מדברת עליכן" -- "Yes, I'm talking ABOUT you."
That's formally the correct way to say both words. See the inflection table in Wiktionary - https://en.wiktionary.org/wiki/%D7%90%D7%9C#Etymology_4 , so if it's a hearing exercise both answers should be accepted.
You're right that in spoken Modern Hebrew, you'd say it differently (elechen vs. alechen).
So the modern pronunciation has changed for the second- and third-person plural forms? I had no idea. Thank you!
Could you also speak WITH someone in Hebrew? אני מדברת איתך? I realize there is a difference between ”to speak to” and ”to speak with”, that's why I ask. Thanks.
No, you can only use the preposition אל with this verb (when adding a pronominal suffix). So:
I am speaking to a cat - אני מדבר לחתול/אל חתול
I am speaking to you - אני מדבר אליך