No where is a daughter mentioned. If Jaim Harlow dosen't respond I can assume he made it up. I will ask expert Jewish geneologist HaRav HaGaon Rabbi Aaron Spira and others in regards to this.
http://www.daat.ac.il/encyclopedia/value.asp?id1=1099
(Translation)
Rav Hai Gaon married the daughter of Gaon Sura Rav Shmuel Ben Hefni. He did not leave any children behind, and died seven years later, at the age of 99.
https://www.yeshiva.org.il/wiki/index.php?title=%D7%A8%D7%91_%D7%94...
(Translation)
Rabbi Hai Gaon married the daughter of the Gaon of the Sura Yeshiva, Rabbi Shmuel ben Hefani, and he had no sons (although in certain sources his son is mentioned, "Rabbi Yosef Maromi"), Avishai Elbaum, families referring to King David Uncle).
https://he.m.wikipedia.org/wiki/%D7%A8%D7%91_%D7%94%D7%90%D7%99_%D7...
(Translation)
Rav Hai married the daughter of the Gaon of Sora Yeshiva, Rav Shmuel ben Hefani, and he had no sons (although in some sources son is mentioned, "Rabbi Yosef Meromi").
