Generally, it is never recommended to glue anything on top of ceramic tile. The reason is the adhesive use may not cure. I understand you need something on a short term basic, and I am thinking something like contact cement may do it. This would not normally be recommended, because it may bleed through to the surface and discolor your liner, but in this circumstance, that may be an acceptable side effect.
Please understand that your entire shower should be redone. Tile on top of drywall is destined to fail, and the entire shower may be in almost as bad shape as the tiles around the window.
It is a good idea to get rid of the window! Remember that building code and common sense will require a vent fan. Get a good quiet one, with a CFM which will give you at least 8 air changes per hour. The higher the better, but low sones rating ( max. 1.0) is very important also.