"Carrie and Rosa"
You're right. The audio is incorrect. There should be no N sound at the end. It's "ruuza" or "rooza" depending on how you want to represent the sound و
The reason for this is that the text-to-speech engine is interpreting ا as اً because ً is commonly dropped. It can't tell that this is a person's name. So just know that there is no N sound at the end in this case :-)
Some Arab countries don't put a space between the word and وَ (which means "and"), and some Arabic countries do (like Lebanon, my country). For some reason, the course makers have chosen to use the standard that doesn't use a space, even though having a space would be a lot more pedagogically beneficial, as well as technically easier to show the definition of each word separately. I'm not sure if the course markers are aware of the existence of both standards, in any case, I think it would be better if they add a space for all occurrences of وَ in the future.
I've found that usually the conjunction is attached to a word in these DL exercises, but at least once it was separate. In most Semitic languages that I have studied (Hebrew, Aramaic, Syriac), the conjunction is connected to the next word. It's interesting to learn from SamirShaker that some countries separate. Thanks for asking the question and to SamirShaker for helping us.
In Arabic, there is a rule stating that "conjunctions and prepositions consisting of only one letters are always attached to the following word". In the case of وَ = and, it is not necessarily visible in both handwritten and printed texts, but it is always the case with other prepositions like بِـ ≃ with, so I guess DuoLingo tried to teach the most 'proper' way of writing Arabic.