i think you have to get there between 4-9 pm on a Friday

It's in the frozen cave. Meditate there until the chest pops up. ;)

Im having this same problem.
The frozen cave thing is where the chest appears to unlock tanya.
But at A3 in outworld, she sets u a mission to fin her a cave to capture Liu kang. This cave is in H5 on ur second visit to outworld. but I cant find her back at A3. ive tried meditating and cant get her.
U can fight her at C3 too. Can u only finish her mission before u have fought her? Help please!!!

*spoiler?*
yea u dont ave to find a cave tho, u have to warn liu kang and he is at that place surrounded by a massive wall cant remember the coordinates.

When I couldn't find Tanya after I searched the caves I found it was because I had found Lui Kang first. However I later found that you get a larger award from Tanya.
I won't save Kangs butt again.....Cheapskate.

Well, I have meditated for a whole week and cannot find Tanya. I also went to the city to speak to Liu Kang and he said, I will speak to u later. But he doesnt. I definitely didnt get koins off him before and havent gotten any off of Tanya either. Whats going on lol.

I had no trouble finding Tanya. First time I got into Outworld I went looking for her and found her in the cave almost straight away. Very easy find. I don't even think you have to speak to Tanya or Lui Kang at all before you find her. Just go straight to the cave as soon as your in Outworld. It will appear.