I do agree he should talk to her but he should also go into the convo knowing he has nothing to lose. You're both checking each other's phone so the trust is already gone. A relationship without trust is like building a house on
Quicksand; you're both going to sink eventually.
I don't buy this "some women aren't direct with rejection". He's her "OLD" pastor. What business does he have contacting Her with inappropriate messages? She should've blocked and deleted him after the first message, no entertaining that bullshit.
And just because it looks like she didn't send a selfie, it doesn't mean she didn't. She's probably more tech savvy than you think. She's not a baby. You don't need to explain to her how it was wrong to carry on talking to him.
The writing is on the wall son.
I think it is obvious that he has nothing to lose & there is little trust on either side, so I agree with the sinking sand comment only if you both had ill-intentions.
To figure out if that is the case, a conversation (without attachments to what the conversation might have meant) needs to be had.
Curiosity needs to rule here. Anything you don't understand, ask her. You guys have a new relationship, so the only way you can learn about each other is to share.
Trust your gut also because it is possible she sent the pictures elsewhere. It is important that if you think that is so, you share that with her so that she now how far your mind has gone. Gauge her response to that idea, then go from there.
It is important to understand that this is not a regular man she was talking to, it was an ex spiritual leader of hers. There is a different type of relationship that people have with their pastor and religious leaders that might make them feel that rejecting a man of the cloth outright is like rejecting God - or uncovering them in their human frailty.
"
No matter what you do, your pastor is going to have at least some charismatic power over you. It’s part of her or his job description.Ministers are, by definition, experts on God-related stuff. They get hired because they can capture the attention of their congregation. They do this by presenting themselves as having some kind of spiritual or supernatural sensitivity—they wear flowing robes, or bless the bread and wine, or explain Bible passages. If they didn’t do
something like this, you wouldn’t be at their church. You could just go and pray with friends (which, by the way, is what Quakers do—they don’t have clergy, and their official name is “the Society of Friends). If you believe that someone has a special sensitivity about God, he or she is going to have power over you, because God is, by definition, all-powerful.
A lot of my non-religious friends particularly didn’t understand this point, so I’m going to put it another way. Think about titles: “Reverend” (from “revere”), “Monsignor” (“my lord”), or, in the Episcopal Church, “Father” or “Mother” (do I need to explain that one?). "
Source:
http://www.thehopeofsurvivors.com/news_notes/11_Reasons_Never_To_Date.php
These are nuances that that exist in some religious organizations that I would not expect everyone to understand, but I just wanted to put that out there.
If she puts him in his place, then it should be over. If he persist, handle his ass. 
