She had given me verbal permission to use the photos for whatever I wanted, but now that we aren't close anymore, she has decided otherwise.

This comment makes the situation a bit more hairy legal-wise. The fact is that the copyright of a photograph always belongs to the photographer regardless of the photo's subject, apart from some edge cases that don't apply here (e.g. a photograph of another photograph or painting), unless the photographer explicitly agrees or has agreed otherwise.

What makes this tricky is that the photographer gave you permission to use the photographs as you see fit, but revoked it later. Owning the copyright doesn't let one retract usage permissions at will.

Whether she is legally allowed to revoke the permission depends on your jurisdiction, and if you were to go to court, the result would probably depend on the judge and how good the lawyers are in presenting the matter. Since there's no written contract, she could also deny ever giving you a do-what-you-want license.

That said, the legality of the matter is mostly irrelevant. Neither of you are unlikely to go to court over a trivial matter like this. What it comes down to is ethics and practicalities: Would it be ethically correct to use the photos against the photographer's wishes? Is it ethically correct for the photographer to revoke the permission she has already granted?

Since you seem to be unwilling to even mention the photographer's name on your web site (otherwise you wouldn't be asking the question), I'm assuming there's quite a lot of bad blood between the two of you. If you do use the photos against her will, regardless of whether it's legally or ethically allowed, how much would it make the situation worse?

In practice I would suggest not to escalate the situation any further and just either credit her on the web site as she wishes, get someone else take photos of the dogs, or spend a couple of dollars on stock photography.