闺蜜 in Chinese means two girls have very good relationship, and much closer than normal good friends but they are not lesbians.
蜜: connotes honey;
闺蜜 could be short for 闺中密友, which literally means the intimate friend in a woman’s bedroom or private sitting room.
The best I can get are terms like besties, intimate relationship. Besties seems like best friends, which can be used for both men and women. Well, 闺蜜 is women only. Intimate relationship seems to connote a romantic relationship like lesbians.
Any other suggestions?