Few years into/after the marriage

Diana, a few years into the marriage, realized it wasn't a marriage of love and it wasn't a fairy tale either. (Marriage is a life-time commitment to a spouse.)
Diana, a few years after the marriage, realized it wasn't a marriage of love and it wasn't a fairy tale either. (Marriage is a one-time ceremonial event.)

Thanks for answering. In general what is the difference between 'into' and 'after'? If I say, "A few years into/after the success of her film", how does the meaning change in general ways?

"A few years into the success of her film" sounds unnatural to me. Even if something is very popular at first, its success is usually short-lived.

Thanks for the reply. I just wanted to know the difference between 'into' and 'after' and hence gave the example. Can you help?

If something can only be considered a one-time event, use "after":

a few years after X = a few years after X occurred

If something extends over a long period of time, use "into":

a few years into X = a few years after X began