So you have to lean over backward to be fair and make her comfortable with the new arrangement. Second, you don't want it to appear that you want her to live with you to reduce your costs, so one way to do this would be for her to simply pay the increased costs of her moving in. You had to pay rent and utilities before, so there is a basis for saying she should only be responsible for the increase caused by her residence in your apartment. And if that's a really small amount, don't count pennies. Couples who try to divide everything up evenly are doomed to failure.
Every outing winds up with a discussion of who ate more.
Since you're already paying the rent and insurance etc. For example, she could pay half of the utilities and groceries along with her personal bills. Or you might consider agreeing to a set amount that her monthly contribution toward expense would be. That way, she'd know what to expect and so would you. Of course if she has relatives in China that she talks to on the phone every night, that should be her responsibility.