Does any reference of Ma Sarswati being reincarnated as another Devi?
As per Shiva Purāna: Umā-Saṃhitā: Chapter 48 - The manifestation of Sarasvatī, the goddess who was slayer of Śumbha was an incarnation of Sarasvatī:
Thus was the goddess, slayer of Śumbha born. She is said to be Sarasvatī. O king, she has manifested herself as a part of Umā.