Use your wife’s charger and MagSafe cable. Will work just fine.I have the 35 watt charger. It's not super fast. My Wife has a MacBook Pro with Mag safe as well.
If your wife has a 14" MBP, it shipped with the 96W Power Adapter
Yes, but if you use it at the same time as you are charging it, you will use more battery charge than the power adapter can supply, so a net loss. Charging MBA will take a long time if let it sit, but it will charge.Is it possible to charge the MBA from a 12W USB charger via USB-A to USB-C cable?
if the charger brick has a USB-C port then it's compatible.
i use a 40W anker nano pro. for me 40W is enough and the charger is probably as small as you're gonna get.you want more power then it's gonna be bigger.
edit: apparently the nano 2 can do 65W and is about the same size.