Her smile felt so brittle she was certain it would crack at any moment.

Her smile was feeling more and more forced with each passing second.

Her own smile felt wide enough to split her face.

I was smiling, but the smile felt much too wide.

His smile feels more natural as the chill of the glass fades.

Nick smiled, but the smile felt cold on his lips.

He was smiling, but the smile felt cold and false on his mouth.

The smile felt like a mask being pulled down over her face.

The smile he managed to produce felt ghastly from the inside, but seemed to look good enough.

His smile felt more relaxed than he would have expected.