Where are you from? I’m proud that women can relax so much that they go shopping in another country. I recommend the Kanyon Shopping Mall. It’s huge! There’s also Metrocity next to it in case one mall isn’t enough. As for a car, I recommend booking one on the website https://gettransfer.com/en/directions/turkey/istanbul/airports/sabiha-gokcen . My colleague’s parents recently visited him at the hospital, and they rented a car at the airport for 500 lira per day. Of course, in addition to the rental fee, you also need to budget for insurance and fuel.