Work question

So my morning client today cancelled on me last minute this morning so I only had one job today for 2 1/2 hours. This is not a good week for money already. 😫

So here's my question for all you readers. Do I charge a late cancel fee? This really hurts my bottom line and then again, I don't want to put her out $20 (£15).

So please let me know your thoughts in the comments below!