Adverb usage: tight/tightly

I'm new to English. Could anyone tell me what is wrong with the first statement?

1. She held the bag tightly, even her arm hurt badly.


2. She held the bag tight, even her arm hurt badly.  (Correct one according to a source)

Answer

Sentence 1 uses the word tight correctly.

She held the bag tightly, even her arm hurt badly.

You need to add "ly" on tight to make it an adverb. The word "tight" is describing her hold on the bag—not the bag. Holding is a verb, so an adverb should be describing it.

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However, the rest of the sentence is not correct. It should be either separated into two or the second part changed to a dependent clause.

These both work:

She held the bag tight. Even her arm hurt badly.

She held the bag tight, even though her arm hurt badly.

Edit: As the other questions point out, "tight" can also be an adverb. As a native speaker, using tight as an adverb sounds a little odd, but both sentences are correct.