$45000 for 5 years comes to about $173 per week.
You couldn't get a hooker or a housekeeper that cheap.
I'd give her the $45,000.
The alternative is a hostile divorce that could take a year or two and cost you $20,000 in lawyer fees on the chance that you might cut that in half.
Couple of things to do BEFORE you actually file for divorce while your credit rating is still good.
Each of you apply for individual credit cards. Pay off or transfer the joint balances to the individual cards in whatever split you decide.
If you have joint car loans, pay them off or refinance into individual names before and sign over the titles to each other.
Refinance the house into your name and get her to sign the deed over as part of the loan closing. If you make about 50K per year you shouldn't have any trouble qualifying for 111,000 on your own.
If you owe or own anything jointly after the divorce, well, you just need to read back over the divorce boards to see what kind of nightmares can result.