The only difference (between Devaki and Yasoda) is that Devaki was able to understand that the SP of Godhead had been born to her and had now changed into Krsna, whereas Yasoda was not able to understand what kind of child had been born to her

Expressions researched:
"The only difference is that Devakī was able to understand that the Supreme Personality of Godhead had been born to her and had now changed into Kṛṣṇa, whereas Yaśodā was not able to understand what kind of child had been born to her"

Srimad-Bhagavatam

SB Canto 10.1 to 10.13

Nanda Mahārāja and Vasudeva were intimate friends, and so were their wives, Yaśodā and Devakī. Although their names were different, they were practically nondifferent personalities. The only difference is that Devakī was able to understand that the Supreme Personality of Godhead had been born to her and had now changed into Kṛṣṇa, whereas Yaśodā was not able to understand what kind of child had been born to her. Yaśodā was such an advanced devotee that she never regarded Kṛṣṇa as the Supreme Personality of Godhead, but simply loved Him as her own child.

SB 10.3.53, Translation and Purport

Exhausted by the labor of childbirth, Yaśodā was overwhelmed with sleep and unable to understand what kind of child had been born to her.

Nanda Mahārāja and Vasudeva were intimate friends, and so were their wives, Yaśodā and Devakī. Although their names were different, they were practically nondifferent personalities. The only difference is that Devakī was able to understand that the Supreme Personality of Godhead had been born to her and had now changed into Kṛṣṇa, whereas Yaśodā was not able to understand what kind of child had been born to her. Yaśodā was such an advanced devotee that she never regarded Kṛṣṇa as the Supreme Personality of Godhead, but simply loved Him as her own child. Devakī, however, knew from the very beginning that although Kṛṣṇa was her son, He was the Supreme Personality of Godhead. In Vṛndāvana, no one regarded Kṛṣṇa as the Supreme Personality of Godhead. When something very wonderful happened because of Kṛṣṇa's activities, the inhabitants of Vṛndāvana—the cowherd men, the cowherd boys, Nanda Mahārāja, Yaśodā and the others—were surprised, but they never considered their son Kṛṣṇa, the Supreme Personality of Godhead. Sometimes they suggested that some great demigod had appeared there as Kṛṣṇa. In such an exalted status of devotional service, a devotee forgets the position of Kṛṣṇa and intensely loves the Supreme Personality of Godhead without understanding His position. This is called kevala-bhakti and is distinct from the stages of jñāna and jñānamayī bhakti.