i’d definitely recommend El Calafate and Los Glaciares National Park, The Perito Moreno glacier is stunning. The Northern section of Los Glaciares is fantastic for a day hike - el Chalten is the town where you base yourself, then you can do a short hike (longer ones are possible too, obviously) where you can view Cerro Torre / Fitz Roy peak.
I wasn’t keen on Bariloche, but I wasn’t well when I was there so that may have been part of the reason for my ambivalence towards it.
I thought the Talampaya and Ischigualasto parks were absolutely stunning. As far as I remember (it was a few years ago), we based ourselves in mendoza (but it may have been SAN Juan) to visit those parks. I really like Mendoza and we just picked up a flier for a trip to the parks - turned out that it was a 2 day trip and my friend and I were the only ones on the trip! The parks are UNESCO world heritage sites. Ischigualasto is known as Moon Valley because the landscape is quite eerie and weird. Talampaya has giant red sandstone cliffs - almost like a smaller, much less visited version of the Grand Canyon.
I really liked Salta - I felt the towns and cities further south felt very European but Salta felt much more Quechuan. From Salta you can visit the Quebrada de Humahuaca and travel through the cloud forest.
Iguazu Falls - stunning.
In Buenos Aires, I really liked the SAN Telmo district and the bookshop that used to be a theatre. The art museum was great too. We did a trip just outside of BA to the Parana Delta which was lovely - a collection of islands separated by streams and rivers.
It’s a really beautiful country with fabulous food and wine. I hope you both have fantastic holidays!