I'm assuming you both file separate Schedule Cs.
There's an option (see below screenshot) that allows you to choose that you share your office.
Answer the questions until you get to the size. You'll need the size of your home and office, estimates are okay.
As long as you're both using it to produce income, then you can both take the deduction on your own Schedule Cs.
As far as your internet expenses, you'll have to estimate the percentage of business usage.
She will be able to deduct the cost of her new computer. The 99% usage is close enough to 100% to depreciate the entire cost (or Section 179, it depends on what your income forecast is for next year).