#fembastian

I think fem!sebaciel would become entangled emotionally very quickly (not necessarily healthily heh), moreso and more obviously than their male counterparts, and they might even throw around the word "love" in a way their male versions would not. Not that fembastian believes she is capable of love, but (assuming she also cannot lie) I think she would enjoy using the word in a manipulative or pointed fashion to tug at her mistress' emotions, and for her own selfish reasons, to encourage fem ciel to open up and show vulnerability if not affection (kind of like how male sebastian tries to get ciel to open up, but he does it differently and it's not necessarily about engendering affection from his master). fem ciel would still be cold and closed off and mistrusting of the demon, but I think she would eventually become more receptive to fembastian's emotional wiles and especially in her more vulnerable moments give in to embraces, cuddling, running fingers through her hair, etc. (whereas male ciel more quickly rejects those things)

fem!sebaciel together would occupy a different space in society as women, so fembastian would not be a butler - she would be a housekeeper, lady's maid, and governess-in-one. And fem ciel would still be considered the head of the Phantomhive family but only due to the lack of a male heir, which would put an even greater burden on her in terms of taking up the mantle as Countess Phantomhive and Queen's Watchdog. I think fem ciel would struggle even more than male o!ciel, in terms of proving herself, because she would be dismissed as a silly young girl by many (though ironically maybe not by the Queen, a woman herself who was not originally expected to take the throne - I almost wonder if victoria would be more personally invested in fem ciel as a subject and leader as compared to o!ciel - like she is very interested in sieglinde in the canon). It's also possible fem ciel's struggles as Watchdog might mirror those experienced by her grandmother Claudia, and she might think about/talk about her grandmother more than o!ciel does.

I also wonder if would fem ciel would still start the Funtom Corporation, or if she would work with fembastian to do something different to bring joy to children and/or help them, perhaps by establishing Funtom more as a nonprofit foundation, and use it as a means to disrupt or upend the existing despicable world of philanthropy/charity (an area in which it would be more acceptable for a woman in fem ciel's position to take up a significant role), to pull up the veil hiding nobility's misdeeds. fembastian would probably agree with exposing the hypocrisy and would help fem ciel leverage her position to do it.

fem ciel would ultimately surprise everyone including fembastian with her strength, but she would perhaps not be "tough" so much as brittle, and easily exhaust herself, and would feel deeply the injustice of being a woman in this world, and she might cry a lot and/or rage about this -perhaps with complicated feelings towards her mother Rachel and/or Aunt Angelina for not preparing her enough for this life, maybe feeling envious of her cousin Lizzie for having Francis train her to use weapons and urge her to show strength - and this would bring up feelings of personal inadequacy including all the times she felt overlooked in favor of her older twin sister - though she would hide these outbursts from everyone except fembastian, who would be all too happy to comfort her (enjoying the dependency her mistress has on her) and feel great satisfaction and possessiveness in doing so. fembastian might see an opportunity to take up the mantle where fem ciel's female relatives failed her.

While fem!sebaciel's womanhood would present certain challenges when moving through society, I think it would simultaneously allow them greater ease when engaging in close interactions between themselves - because they are women they could more easily avoid certain accusations of inappropriateness, in that they could be a bit more blatant with invading each other's personal space, with affectionate touches, general closeness and so forth. fembastian would especially take advantage of this, easily making their interactions seem like nothing more than a lady's maid taking special care of her noblewoman (nothing scandalous to see here…)