the other day my girl came over and said here 8830 sprint was messing up so I saw a new os for it was available so we upgraded fixed all the problems and now i need to reactivate her BES service on her phone

Tell her to contact her IT Department and ask them to provide a new activation password for BES.
Hopefully, you didn't just get her fired.
Might have been wise to let her company deal with the device, since you don't really know what you're doing.

no not fired but really pissed at me right now dose she just need to get the password and enter it on her phone through the bes setup

She needs her BES admin to set an Activation Password for her BES account.
Then she needs to take that password and do a wireless Entperise Activation on her device.
Her IT department will explain the process to her. Perhaps it's best that you removed yourself from this process. You should encourage her to contact her IT department to fix this. And then get her flowers.

yeah i need more than flowers she just told me her it guys out of town for the next few weeks

if i still have the backup of her old could i just revert her phone back to the old os and then just load up the backup that i have or could i just get away with just loading the old backup file

Nope, a restored backup won't work.
Once the device is disconnected from BES, the only way to reconnect it is to do a new Enterprise Activation.

In some cases doing a wire sync with desktop manager online will active the device on the BES. Worth trying that option