Hmmm, why would you wanna give her anything, let alone 50/50. As soon as she finds out your gonna split anything she will be expecting 90/10 on her behalf.
If i was you i would try and get what funds you can together,slowly, and place them in a trusted friends account and plot your departure.
Make out as though your trying to make a go of it, not letting on that you want to split. As soon as you have enough funds then do what you say with what is left. I know it will be hard to live with her during this time but it will be worth it in the end...