Hmm... so she won't let you use it as a planter, and she won't let you sink it into the ground as a pond... but she's happy to see it sit there covered... which must mean that in some part of her mind she's thinking it can come back to life as a hot tub...

Hmm...

Well... all I can do is tell what I would do.

I'd plant some shrubs around it, but still leave the steps into it open, and I'd fill it up with water, and I'd go a local pond and scoop out some buckets of mud in order to get a good sampling of all the little microranism that live in ponds, and seed them in there, and I'd seed it with fresh water shrimp, and I'd also collect a whole bunch of pond weeds, and sow those in there, and then I'd got to a fish hatchery and buy some rainbow trout fry, and plant them there... ranbow trout can live and grow in still-water about as deep and wide as hot tubs get.

I'd let them feed on the fresh water shrimp, or toss in fish pellets (guinipig pellets, or dinner leftovers will do too) if it looks like they're not getting enough from the fresh water shrimp, or if they've eaten the shrimp to extinction, and when they get big enough... I'd start fishing for them... you know... flyfishing from behind the bushes that were planted around the tub... or maybe play games, like... walk up the stairs to the edge of the tub and see if I can catch them with my hands.

That's basically what you're thinking of... turning it into a fish pond... only without half burying it... just ringing it with shrubery, and she can't say that you're turning it into anything that could not, in theory, be turned back into a hot tub, but by ringing it with shrubery, you've fixed the eyesore aspect of it.

You might get lucky and have some mallards adopt it, and you can even have a fishing party with your pals, only with easy access to the fridge.

That's what I'd do.

Or you can check and see if your area has a Yahoo freecycle group. You can then put a free add on an internet community board with freecycle and someone who wants it will come get it for FREE!

Have you tried selling it? Someone might buy it is it's repairable.

I think the Norwegian pine is the easier and more hilarious option. I would love to see pictures after you plant a pine tree in a hot tub.

I cant see a pond made out of a hot tub looking very natural. The maintenance is going to be kind of a pain too. You have to worry about mosquito breeding and water filtration. If the pump is busted on the hot tub you have to get some kind of pond filtration system.

Go with the tree. No sense in keeping the hot tub there with no utility if it doesn't work.

I don't think planting a tree in it will work unless you punch some holes in the bottom to allow excess water to drain out of the soil. Sinking it in the yard to make a working fountain would also be difficult, because the pumps are down on the side of the tub and would have to be underground. A hot tub also seems like it would be too bulky for either of those options to really look good.

Allowing it to sit around empty doesn't make much sense though, and it's probably an eyesore (and getting worse daily) which is why you're impatient to do something with it I'm sure. If it's repairable you could put it on Craigslist and see if someone will take it away for free, but otherwise you might just need to get it taken to the dump.