Jungle can get infested now as of recent patches. However, hallow will leave jungle alone.
As per the original question: the hallow stripe extends into the snow biome. Sadly, this will mean having to buy hallowed seeds from the Dryad and planting them on the surface on bare dirt and allowing the Hallow to spread. My choice for this is a fair distance from the surface contact of the evil spread.
When you get an incident like this, where the hallow goes towards snow, your primary focus should be to try and get a gapstop set in place before the jungle, because of said infection.
Some future preventative advice for people here though. One thing I recommend doing before setting off hardmode is to have a good sequestering of your 'home spot' with a 5-block gap, then lined with any easy-to-make brick. The same thing should be done before the jungle, but in more of a one-sided hellevator well effect. Bring obsidian skin potions; you will have to deal with lava. Once you have that set, line the edge facing away from the jungle with easy-to-make brick.
Why brick? It not only allows for a more subtle marking of what the bounds are, but bricks can't be corrupted.