Are you absolutely sure lease cannot be extended? I would wait. Unless you leased it without W knowing anything about it then she is well aware of the sitch.
She will bring it up eventually, but if she doesn't then cross that bridge in the spring.
Right now it would look like you are envisioning a future together and it may scare her silly. You don't have to move tomorrow, so it is not worth stressing about today or even next month.
You can plan for your own future for sure, by putting a down payment aside (if you can) but if it were me in W's boots, I would honestly think you we're discounting all my feelings by making future plans. Just give it a bit yet.
So, my partner in not texting every five seconds....shall we see how we do? :p
