This is best shown by putting the chapter into outline form, with the relevant verse numbers indicated in brackets.
Men's vows stand 
1. Before marriage (in father's house) 
2. Status during marriage of vows made before marriage* 
3. If divorced or widowed - vows stand 
4. Vows made during marriage 
Husband has power to allow or nullify 
To allow 
To nullify 
* Or else, this could be talking about vows made after engagement but before marriage.
Looking at the chapter this way, it is clear that the only possibly repetitive section is verses 14-16. It is not absolutely clear to me what the function of this section is, but here are two suggestions.
Perhaps, since the "normal" case of a woman's vows being nullified is by her husband (girls generally got married shortly after they became mature enough to make a vow), this section is just a summary of the laws of vows using the most common case.
Alternatively, the description of the vows in this section is more detailed than in the other sections - כל נדר וכל שבעת אסר לענת נפש. So while the previous sections teach how and when vows are nullified, this section teaches which vows are nullified.