Login to Admin Panel

My wife has a website built and set-up on a domain. She is re-branding and therefore switching domains. I went into her admin panel and switched the domain, but then realized that because I had just registered the domain, I couldn’t assign it yet. I switched it back to the original one and saved it.

Now — her website is not working at all. The layout is messed up and it won’t actually load any of her pages. Also — trying to login to the admin panel — it says that it is unavailable. It tried to redirect to the new domain name – even though it was never actually registered. It won’t let me login to the admin panel. Obviously the new domain isn’t set up, and it continually tries to redirect to the new domain. I need some way to override that and login to the admin panel again. Help!