彼女は何度も納期を守れなかった事がある
There were several instances when she failed to meet our deadlines.
⚫︎〜だったことがある
There were an instance when...
⚫︎someとseveral
ぼやっと→some
具体的に例を言える→several
⚫︎didn'tとfailed to
事実報告→didn't
残念、懸念(気持ち強調)→failed to
⚫︎納期(締切日)に間に合わす
meet deadline(s)
※何度も納期に間に合わなかった→deadlines