It really depends on the whole relationship. There's 3 ways you can see a woman's pussy shot:
1) One of them shows you with the consent of the other because of their cuckold or open relationship. This is a sexy hotwife and is common.
2) She shows it to you without her husband's knowledge. Some would call this a "cheating slut" and some would call it an "unknowning cuck" situation. Either way, the husband may not be happy when he finds out.
3) Husband shows you without wife's consent. This is common in my experience, and stems from a number of things: husband is showing off, husband is turned on by the comments, husband is sexually confused, etc.
I can't say which is more common, since there's a lot of fakes, single girls, and internet pics floating around. Though I can say that I've encountered all 3 of the situations above, and even within those 3 there's plenty of nuances.