In one location I have renewable power, at my friend's place, but the internet is filtered, so p2p/geth seems to be blocked.
At home I have unfiltered net.
Is it possible to run geth at home (Windows), but mine at her place (Windows)?
In order to mine, you need to build on currently existing blocks and transactions. Therefore you cannot mine offline.
From your mining machine you could however create a VPN or tunnel to some machine that is able to connect to other nodes as described here. Otherwise you will not be able to create blocks that will be accepted by anyone else in the network (and you wont get usable block rewards).