Is there a way to open a window that has been glued shut?

If it is Elmer's Carpenter's Glue, then just keeping the area saturated with water may help. Elmer's Carpenter's Glue isn't made for outdoor projects because it's not waterproof. If you think it's Elmer's glue, the water may do the trick. If the glue isn't Elmer's Carpenter's Glue, you're likely wasting your time with the water. If you can get a small bit of the glue free from the window, you may be able to test it in a few solvents to see if any of them are able to soften it up or dissolve it. Then, depending on the solvent, you may be able to use it to soak the bottom of the window to get the glue to release. Your wife's idea probably isn't feasible. If you could pour water under the window, it wouldn't be stuck in the first place. Let's hope there's just glue on the bottom and not on the sides too! Be careful if you try a heat gun! You could either break the gl with the heat or start a fire! If none of these tactics work, you may just have to keep working a thin blade knife of some kind between the sill plate and the window to "break" the glue seal. If you can get in touch with the previous owner, you can ask them what material was used. I'm out of ideas for now. I wish you luck with this project!