Humping is not just hormonal behavior, it is also a dominance behavior. Though spaying will most often decrease humping behavior, it doesn't get rid of it completely because this is how rabbits establish who is in charge. You need to allow a certain amount of humping to occur for rabbits to be able to establish their hierarchy. If it gets to be excessive, such as going on for more than 15 seconds, then you can
gently stop the rabbit from humping. Spraying them with water really isn't the best thing to be doing. Just gently slide the bunny off with your hand or pick the bunny up and set to the side. You will likely need to do this many times, as humping can continue until they sort things out between each other. Circling behavior you don't want to continue as it often will lead to fights, so you want to stop it right away. Using gloved hands as you could very well get bitten intervening.
You also should move back the bonding process to the neutral area where you started it. Changing bonding areas can set you back in their progress, as can increasing area size too soon. Also if Snowy has been in your room, she may consider it 'her' territory, and this can further lead to territorial behavior and more aggression.
In a few rare cases, unspayed rabbits may get along and bond alright. But more often the hormones will lead to fighting. Best thing would be to get both does spayed. 6 yr.s isn't too old to spay a rabbit. Being older does make it a bit riskier, but as long as you have a blood test done to ensure good organ function, and have it done by a really good rabbit vet, most likely it will be just fine. Also as a rabbit gets older, they are more at risk of developing uterine cancer, so spaying for that reason is also a good idea. Spaying won't eliminate humping or aggression, but it can help calm it down so it's not as excessive.
If you don't want to get your older doe spayed, you may need to just wait on the bonding process until your younger doe is spayed, then wait 2-4 weeks post spay before trying again. But just be aware that trying with even one unspayed doe does somewhat reduce your chances of success and increase the risk of fighting.
It's also a good idea to read up on bonding techniques so you know what behaviors to expect and how to deal with them appropriately.
https://www.facebook.com/notes/the-rabbit-crossing/my-guide-to-how-i-bond-rabbits/463430373700695
http://www.wheekwheekthump.com/2013...rs-guide-rabbit-bonding-everything-need-know/
http://cottontails-rescue.org.uk/information/bonding-bunnies/
http://flashsplace.webs.com/bondingbunnies.htm