Each entry is at the discretion of cbp. How is she able to afford to travel with such frequency? What ties does she have to return to her country at the end of the authorized stay?
I think you're getting too confident coming on a visit visa. Have your significant other visit you in Europe a few more times or meet in 3rd country before filing for k1 or cr1
Your first post wasn't very clear. If you had said I have my expiring green card and original 48 months extension letter, I would have answered differently. You said "extended 10 years pending biometrics ". A 2 year green card is either extended or not. I have seen the extension letters frequently in my line of work and the letters are very clear.