Hi caitlan132,
Thank you for using the Apple Support Communities! I understand you are experiencing an issue with the backlight on your MacBook Air. I'd like to assist.
You mentioned already taking your MacBook to an I.T. related store who determined it is a hardware failure likely, but did not mention what steps were attempted to troubleshoot the issue. The articles below could help troubleshoot the issue:
-Change your Mac display’s brightness - Apple Support. "If your Mac has an ambient light sensor, you can use it to adjust the screen’s brightness by selecting the “Automatically adjust brightness” checkbox in the Displays pane of System Preferences."
-How to reset the SMC of your Mac - Apple Support. This can help when it comes to sensor issues, such as the backlight.
If the issue remains, I would recommend having your MacBook Air inspected and evaluated in person at your local Apple Store Store List - Apple Store - Apple, or Apple Authorized Service Provider Apple - Find Locations - Location Selector. Or, reach out to discuss options here: Contact - Official Apple Support.
Best regards.