It is hard to comment when the window is not shown in context of the room. Is there a way to make it look wider by including wall area on the sides? Is it over a toilet? Will you miss the light if you put a opaque shade over it?

The window is next to the toilet. Here's a pic of it before we renovated the bathroom. The window is the same.

How about a

How about a short sheer curtain?

Ignore your family! LOL Or here is an inexpensive idea: I used a sheer gathered top and bottom with spring inside - mounted (easy to install) rods. Bed Bath and Beyond. It looks like your window could have space for that. You should get one that is at least 2 times the width of the window. The more gathers, the less you see in or out.

I love the idea (of ignoring my family, LOL!) Where did you get the small curtain, or did you make it yourself?

How about a metallic micro mini blind mounted inside frame. You could raise it up when not needed and it would disappear. I do understand the feeling of no privacy even tho the glass is frosted, especially at night.

A light filtering cellular shade would work well there. The stack wouldn't be too big at the top when the shade is raised up.

You want a top and bottom rod pocket sheer curtain. They are often used on sidelites or glass doors, but come in different lengths. I think BB&Beyond, JCP or even Home Depot may have them. Under $20

A curtain is the easiest and most economical solution. They are very home-like. Cut ribbons can be sewn to the top, then tie it onto the rod. Or buy a pack of clips to hang on the rod and no sewing is needed.
Bamboo matchstick blinds are pretty, too. Buy off the shelf and cut it to fit with a jigsaw. Reattach the hardware from the part cut off.
Roller shades can be cut down at home, too, The end pops out and reattaches.

You can purchase Made to measure which at not too pricy at Lowes or HD when on sale. That way you will have something that enhances as well as adding privacy. IMO a sheer curtain doesn't really add more privacy at night when lights are on, even tho you only see shadows.