If he cannot be found, she will be responsible for the $18,000.
How awful
This is the whole point of posting a bond, is that you’re vouching for them and putting your stuff/money on the line that they won’t skip their court date. Posting a bond is like saying you trust this person so much, that you’ll be responsible for them until court. You’re promising the courts that they will show up, by vouching for them. If they skip out and can’t be found then you’ll have to pay the full bond.