I would like to put my wife as an authorized user on my Amex, her credit scores are in the low 600's with a couple collections, will this effect my score in a bad way? Or if anything will this only have an effect on her? All my accounts are in good standing btw.
I know what you mean.
Only the activity in that SPECIFIC card affects your and your wife's credit scores. This means that if you ask for an additional CLI and you get an inquiry in your report, her credit score remains un affected.
If your wife puts in a lot of activity and still rports a 0 balance , then it is good for the card. Which means its good for both of you.