A lot of mums are freaked out by things that are out of the 'norm.' As hammock-hangers, we understand that. If she is the kind who likes to be trendy and fashionable and gets her ideas from 'what everyone else is doing' as far as home design goes, you may just have to do the outdoor thing and wait till you get your own place.
Five months may seem like a long time to have waited already, and it may seem unfair to you, but believe me, it's worth it to keep the peace with your mum.
Real Freedom lies in wildness, not in civilization. ~ Charles Lindbergh