First of all, contact the realtor/landlord directly and ask about the keys because it’s weird they’re only going through one tenant if both your names are on the lease. Second, sit your friend down and get the specifics of what their plans are and shut down parts as needed (telling her the boyfriend can’t move in for example). Honestly if it’s too much for you to handle this is probably the best time to back out and break the lease/transfer the lease to the boyfriend.