Here is the original item:
As Alex navigated the narrow row of
chairs. (A)
His heavy book bag bumped the large soda perched on Teresa's
desk,
(B) sending
a shower of diet cola into the girl's
lap,
(C) soaking
her jeans.
You wanted to do this:
As Alex navigated the narrow row of chairs. His heavy book bag bumped the
large soda perched on Teresa's desk, sending
a shower of diet cola into the girl's lap soaking
her jeans.
Removing the comma after lap is an error. Soaking her jeans is a participle phrase. You will often use a comma to connect a participle phrase to the end of a sentence.
You might want to review the rules.