Regarding the vedic prediction, maybe it's because you have Saturn in the end of 6th, your saturn return happens right before crossover into 7th house of partner. Is your partner a responsible person?
Saturn isn't at the end of her sixth house in Vedic. Vedic astrology uses whole sign houses and places everything 23-24 degrees earlier than Western. The Vedic version of her chart would have Saturn around 5-6 degrees of Aquarius, so not at the end of a house, and since 23-24 degrees earlier moves her ascendant to Leo, Aquarius is her seventh house in Vedic, not her sixth.
Possibly, Saturn in the seventh would make a Vedic astrologer say don't get married until after your Saturn return. Especially when Saturn is also the seventh house ruler, which it is if the seventh house is Aquarius and only traditional rulers are used. That would tie marriage to the Saturn cycle. If marriage is tied to the Saturn cycle, a Saturn return spells the end of a marriage or the beginning of one--or the end of one marriage and beginning of another.
Or, simply, a profound change within the marriage. A transition to parenthood would be that kind of change. And a Saturnian change at that: taking on more responsibility, gaining more authority. Saturn is a parental archetype. To become a parent is to take on Saturn for yourself. Which is exactly what Saturn transits ask you to do.
I don't think the root of this fear is so much fear of divorce in and of itself as it is recognition that becoming a parent means the marriage
as it is will end. It will have to become a very different kind of marriage from what it's been so far. That's a perfectly normal transition to make, and it's also perfectly normal to be afraid of it.
All of that is, right there, Saturnian stuff. Saturn is an initiator. Saturn is a point of no return. Whether you choose it or not, it's coming. So you might as well choose it.