In all seriousness, internet forums are a very poor place to get legal advice.
Just like hiring a cut-rate photographer for crappy pictures, free internet legal advice is worth every penny you spent.
I spoke with R and she explained that she couldn’t get a photographer to shoot her wedding because anyone she contacted wouldn’t call her back.
My guess is because she offered them $100. I wouldn’t call her back, either.
In any case, if R has a shared copyright, you don’t even have to list credit. But if R doesn’t have the copyright or rights to create derivative works, then technically you’re not allowed to edit them. If all she has are print rights, you are fucked. My guess is that R (not you) should make a written agreement that it’s a shared copyright, and agree that any copies/edits will credit “Photo by ###” and no more. You can add Edit by ### or not, or whatever. If the photographer wanted to mess with you and you don’t have this in writing, she can make things difficult, but it would cost her a lot more than the $100 she made; and because she values her work so little, one could argue that the liability should be tiny. Even if she doesn’t file a federal lawsuit, the bad PR and enemy you’re making isn’t worth it. Just get her to sign over the copyright in writing, and you’ll agree to add “Photo by her” on any albums or the image directly, and be done with it.
And you should actually consider talking to an IP lawyer. More and more are cropping up these days, and they’re giving good prices.