She may love gray but it's already on its way out, and it's a difficult color to decorate with at best. She'll be much better off with warm white walls and a light to medium-toned wood-look floor. With that palette her couch will fit in perfectly and she won't be kicking herself for having chosen something that's already so over. Accent colors are wide open, navy blue, terracotta, turquoise, it depends on what she loves - again not what she thinks is trendy. Trends come and go, what you love will always look right.

Is the build ready? or there are things that can be changed yet?

one can decorate successfully with gray walls, using a lot of tonal variations and textures, and light/bright colors against the gray backround-it's much like with gray sky..if it's vast gray sky it often be perceived as sad..bad weather sad. If you put against it trees with all sorts of leaves on it, from green to amber, and happy colorful umbrellas-you see that sky differently, and the rainy day becomes a day to be fascinated with.

it's harder to decorate when everything's gray..so gray wood-like tile will serve here as a little overkill. especially as few woods irl read as gray. result-can look a bit artificial. depends.

photos-if you have them and willing to share-would be really helpful

because one person says "gray"-and another has a mental picture of that gray that might be right or wrong. There are hundreds shades, in every color out there. Darker, lighter, warmer, cooler..just naming a color is not enough. in this case

Same thing with brown. There are hundreds of browns. Cognacs and milk chocolates will look nicer against gray-theoretically-than some dark espresso. They will read warm and will provide contrast. Espresso can make interior gloomier.

Now, one can love gloomy and stormy too. Everybody's different. Whatever makes me happy is not universal to other people-and vice versa. In terms of colors.

But then one must know what he loves, and it demands not less level of consideration, to pull it out.

It can't be "paint by numbers". It's a house -whoever lives there should be happier, or calmer, or inspired, or energized, or relaxed, or all sorts of things one wants from his house.

So she needs to find her own personal balance.

I suggest -if you can't attach the photos-to look for inspirational photos, maybe give us ideas what appeals to her..analyze-what colors are inside? do they work together well? why? what they are remincent of? what is her visceral reaction to them? if the build is ready-she has some givens, right? how she can work with them to still get the feeling, the vibe, she wants her house to give?

Is the house leaning modern or traditional?

What are her favorite stores and sites-prices not important right now, just as inspiration?

Will there be rugs? Window treatments? Does she have them already-or not yet? Anything she's driven to, in farics and soft furnishings?

Does she love patterns? If yes, which?

Light fixtures? What will these be?

Soft lines or hard lines?

How would she describe her style?

So many questions to ask. As much as colors are important-and they are, so very much-good rooms are more than a sum of colors put together.

She can stumble upon her preferred pallette any day.

Happenned to me. Saw a picture in a book. Somehow stuck with me.

At some point I saw the colors together in a different context-and I knew.

Then I added to it/built upon it.

I'm sorry if that advice is vague and doesn't tackle the question in a precise way. That's because I believe -it's important to know the context before answering. General question-general answer. Can be enough. But. The more we can understand though-about the house, about the preferences, about the goals-the more specific we can be, the more we can contribute. The more she knows herself and what she wants to achieve with the house-the better.

If she loves the gray colors, she should have gray in her home. She can absolutely combine a brown sofa with gray walls, and this picture proves it beautifully.

Restoration Hardware seems to love that combination...you might want to take a peek online or get a catalog for inspiration...