The best shapes of glasses for small faces will be short shapes, not tall shapes. 

Small faces are easily overwhelmed by too much frame height. When you shorten the lens height, you naturally end up with shorter shapes. 

Favor short shapes:  Rectangular, oval, and classic cat-eye 

Avoid tall shapes:  Square, round, or contemporary cat-eye 

Also known as half-rim, this style has no material on the lower half of the frame, leaving the lenses exposed.

This is a great option for small face ladies. Less rim means less material to crowd the limited real estate of your small face.

This virtually eliminates the common complaint of lenses with too much height. Since there is no lower rim, the height of the lens is less obvious. This creates a subtle, unobtrusive look similar to rimless frames, but can have a more stylish look thanks to the upper rim.

Since the lower rim is absent and the lens height is therefore less obvious, this also means you can get away with more lens height than you could on a full-rim frame. This is helpful for bifocal or progressive lenses which require more lens height to accommodate the prescription.

Also, the top-heavy shape of half-rim glasses catches the eye at the top, creating the effect of lengthening the face from the browline downward. This has an attractive, balancing effect on short face shapes, such as round and square face shapes, which are common in women with small faces.

Many people (petite and otherwise) find that black frames make their face look washed out. That’s especially true as we age and lose the coloration of our skin.

If this sounds like you, avoid black frames or very dark brown/tortoise.

Instead of black, try blue or burgundy. Instead of dark brown, try tan or a lighter tortoise. If your hair is greying, grey or silver frames are very flattering.

There is a relationship between color and thickness. It makes sense that thick black frames will be more assertive than thin black frames, simply because there’s so much more of it on the thicker pair.

If you like the look of thick glasses, but haven’t been able to make them work, try a dramatic color on a thinner frame. That gives you the bold look you want, without overwhelming your features.

A light, bright color that is opaque will look very assertive. For example, opaque white, turquoise, or pink will pop off your face. Colors like this might look best on a thinner frame, just the same as very dark colors.

Transparent frames are a popular at the moment. They may be totally colorless, have just a hint of color, or rest halfway between clear and opaque. This gives the frame a subtle, barely there quality that helps the frames blend in with your face for an unobtrusive appearance. 

Transparent frames can be worn thicker since the transparency makes it more subtle in appearance than the same frame would be in an opaque color. Also, you have a little more wiggle room on the shape, since the shape is less obvious on a transparent frame than the same frame would be with full, opaque color.