You can use an angle grinder, though the cut edge might chip out more than you want. Although, it looks like a ceramic tile, and already has minor chips in it, so I would just fly at it.
If you do use a grinder, it's helpful to have someone holding a vacuum hose close to where the dust will be ejected from the disc. Can be a bit hard to focus on both making a straight cut, and keeping the vacuum in the right spot, while both machines are screaming at you 😄 It will be dusty in that room, and most of the dust will go into the window, so I would cut a piece of cardboard to fit in that space snug while you are grinding. That should protect the glass from getting any hot dust on it. Careful when wiping, or vacuuming the dust off of the window.