Let's put it this way: صَديق = (male) friend and صَديقَة = (female) friend; adding a suffix leads to صَديقهُ = his (male) friend and صَديقَتهُ = his (female) friend. Since Samia is a woman, you have to use the feminine form of friend, thus صَديقَتهُ = his (female) friend.
This is explained in the Tips of the chapter called PHRASES (on computer, not on phone), and Wikipedia has a lovely chapter explaining the origin of the letter ة and how it transforms into -at. https://en.wikipedia.org/wiki/Taw#T%C4%81%CA%BC_marb%C5%AB%E1%B9%ADah
Thank you for your reply, cohendotan. But my question was whether anyone else could hear the brief, unwritten, fricative sound that preceded ق. As a matter of fact, I feel more confident about mentioning that sound now, because in the nine months since I posted my remark, I have read in some IPA literature that Arabs unconsciously do precede the letter ق with a pharyngeal fricative. "Pharyngeal" is the word usually used to denote what you mean by "throat".
If you notice this course doesn't really care about the content or meaning of the sentence. Duolingo like most Arabs are teaching Arabic through reading. The word gareeb for example is not about the meaning weird but about teaching us the sound g. After we've learned how to read all the sounds in Arabic I suspect the next course or later lessons will focus on greetings, introductions, days of the week, numbers, directions, content that you actually need to say. Think of how a baby learns. They spent a year listening, then they babble small sounds, by 18 months they can speak small sentences, lastly they learn how to read and write. Although I don't prefer this method, Arabic traditionally is taught in an opposite order.