“Actually, swimming 1:05 on 5 months of 6-9000 m/wk is quite impressive. Your GF should be down well below 1:00 in another 5 months, and prob below 55 by next spring. She would appear to have a natural feel for the water. :)”
FFS, yes many AOS swimming 3 x 3k a week can swim 55mins in a year 
Nearly everyone, fit with no physical disadvantages, can get to a 1.05 IM Swim in 6mths with targetted, specific training. Then the plateau occurs. No one is going LCB swim speeds who starts in adult life, no matter how much you do. Well, unless you dedicate 10 years of 30k-70k every week