I haven't looked into it for a while so I'm running off of memory, but that sounds right.
A woman's chance of pregnancy depends on:
- Her Age
- How many children she has already had
- Whether her or her husband have the Virile perk
- If neither she or her husband are the character you're playing as, there's also a penalty based on how many characters (not counting companions I think?) the clan has. Higher tier clans get to have more children before getting penalized
The young wife should have a chance, yes. Unless your clan already has too many people in it, she might also have a chance if you're leaving her sitting in the same town/castle as her husband too.