Nathan came into the palace, not into the chamber, where he might not enter unannounced. Bath-sheba retired before Nathan entered, in accordance with Oriental ideas of propriety. So, when Bath-sheba was again sent for 1-Kings 1:28, Nathan retired (compare 1-Kings 1:32).

And, lo, while she yet talked with the king,.... Just as she was concluding her speech to him:
Nathan the prophet also came in; as he promised he would; perhaps was at the chamber door all the while Bathsheba was speaking, and when he perceived she was just finishing, he entered in without ceremony, as he had used to do, being the king's seer and counsellor, and a prophet, who had admittance to the king at any time.