Your advice matches what other professionals are telling me, Penny.
At this point the best strategy appears to be maintaining communication and trust while allowing her to separate. When she is ready to accept help at least she’ll feel free to turn to us. Setting limits she cannot meet will likely backfire. For me, not nagging or setting limits is difficult; I feel such loss of control and fear. But it helps that she’s talking to me.
Your son is lucky to have you. It sounds like you are giving him exactly what he needs to succeed – even though it takes a lot of effort on your part.