You are NOT REQUIRED, by the IRS, to treat that as reportable income. It is only roommates sharing expenses.
The alternate question is MAY you treat it as income. The answer is not as clear, but, in my opinion, is still NO. The only income types it could be is either rent or boarding house income. From how you described the financial arrangement and the personal nature of the relationship, it is pretty clearly neither.
Even if you were to try to call it rent, be advised that you cannot claim a loss from this activity, to offset other
income. Because of the "personal use rule" (because it is your home, you have "personal use"), your deductions are
limited to your income. Net effect ZERO.
