Welcome bobey miah!! Rexes are beautiful bunnies! I just love their velvety soft fur. I’m sorry your bunny is being such a pain! Unfortunately what she is going though is normal, and this is the time people think their bunny has gone crazy and end up giving their bunny to the shelter. But there are ways to solve this problem.
Like Wendyzski said, it sounds like your rex has reached sexual maturity – usually between 3 – 6months, and this usually is fixed when a bunny is spayed. The sooner the better to avoid bad habits from setting in.
What is happening exactly is that now that she is sexually mature, her instincts are driving her to develop and mark a territory. By doing this,in her bunny mind, it helps ward off other "bunny" intruders who could take her prime spots for food and any future nesting for babies. Also as being part of a warren, all the bunnies will mark certain areas to claim a territory for their group.
With places that hold our smell, like the bed, linens, pillows, chairs and couches, bunnies may feel that we have marked this place and so as a good warren mate, they will too.
The other reason a bunny might mark these areas is to display that they are the dominant bunny and mark OVER your scent. It really depends on the bunny. It does sound like she is trying to claim the couch because she’s digging at it, maybe trying to dig out the human scent, as well as she sprays it so often.
Is she displaying any aggression or grunting towards you at all yet?
Either way, since she is determined to spray it everyday, and not just happy with leaving her scent behind once, then the best way to solve this right now is to clean the couch the best you can, and do not allow her up there at all. You will be the "dominant" bunny by claiming the couch as your own – not just using it as a central marking place.
If she persists, and you can’t leave the couch for a second without her digging, you may need to get deterrents like "snappy trainers" which are these things you can put up on the furniture and when the bunny just hops up, it makes a very loud noise. They scare the bejeebeeze out of me, so I didn’t use them, but my bunnies seemed to be deterred enough with me never allowing them on the furniture by themselves. They can be up there with me, and so far they haven’t peed or pooed while I was up there.
But then again, all three of mine are altered.
Spaying really can make a big difference with this behavior, and not only that, because unaltered females have a very high risk of cancer of their reproductive organs, spaying helps prevent this. And another little benefit, spaying makes their urine much less pungent.
If you intend to have her spayed, we can help guide you in finding a rabbit savvy vet. Which is extremely important – it is not the same as cats and dogs.