She looked this way with a sorrowful expression on her face.
This is a single kanji with an い on the end, but wait! It's not an adjective, it's just a noun (tricky, tricky). The kanji means grief, so this word means grief or distress.
Since this word consists of a kanji with hiragana attached, you can bet that it will use the kun'yomi reading. You learned this reading when you learned 憂える. Remember that and you'll remember this!