Restructure this sentence to avoid a comma splice.
She was exhausted, she hadn't slept since the night before.
She was exhausted because she hadn't slept since the night before.
Complete the following task based on the instruction and optional input provided.### Instruction:
Restructure this sentence to avoid a comma splice.

### Input:
She was exhausted, she hadn't slept since the night before.

### Output:
She was exhausted because she hadn't slept since the night before.