If you are going to eventually need a co-sponsor, I would go ahead with that now. I don't know why one is 100% and the other 125% because once you are married and file for the green card, you will need to show the 125%. Now just to be fair, I don't have experience with your exact situation, but I had thought about that before and I was considering finding a co-sponsor if that was going to be the case for me. Since your mother has agreed to be a co-sponsor, I'd go with that from the get go and save yourself the headache later.
Crazy Rabbit got a reaction from Mrs-Belle in I-134 for K-1 A Little Confused!
Crazy Rabbit reacted to Boiler in B-2 Visa to come to US get married, adopt my daughter, and go back