When to do a big chop?

I’m looking to give this scraggly gal a better shape. I’ve tried notching in the past and it did nothing. I think I’m looking at doing a big chop and starting over. Should I chop her back to just the trunk? Chop the branches back? And when is a good time to do this? We are in zone 6a, so it’s still too chilly to put her outside.

(Yes, I know this is not an ideal location for her. She’s usually directly in front of this window to the left, which is 6×6 and faces south. We’ve had to shuffle some furniture temporarily, so she’ll be back in her spot soon.)