FMCs who likely got the Florence Nightingale effect
Signs:
Seeing the MMC helpless and hurt brings out their nurturing side, a lot of their relationship may have her looking after him and feel disappointed when that aspect changes. The nursing is early in the relationship and that is how the tender feelings developed and come in. Some MMCs also feel more likable when they are too ill to be mean or behave badly.
Examples:
{Trusting Miss Trentham by Emily Larkin} - the clearest example I have read. Seeing the MMC wake up in tears after his PTSD-induced nightmares and looking so lost and helpless gets her nurturing tendencies in full swing. She also bosses him to eat more food, drink sleep medications, reads him to sleep and holds him till he drifts off.
{A Momentary Marriage by Candace Camp} - she guiltily calls herself 'wanton' for enjoying rubbing her husband's chest while he has a fever. She is a doctor's daughter so she is used to looking after the ill and the MMC (who is told he is dying) even mockingly says she found someone to play nursemaid to again.
{Flowers From the Storm by Laura Kinsale} - playing 'nursemaid' comes up and she thinks he does not need her anymore once he sees an improvement (but not a cure) in his speech production and comprehension after his stroke. That thought saddens her - not that he is better but that she likely has no role in his life otherwise.
{The Woes of Wooing a Wife in 12 Days by Mihwa Lee} - she starts off hating having to provide 'intimate care' to her estranged husband but then feels disappointed that she does not have to tend to him anymore. It was actually the only intimacy they had shared up till this point.
While it is not in {Marrying Winterborne by Lisa Kleypas}, this aspect of the MCs' relationship is in the previous book and how the FMC meets him. She is gentle and sweet and he demands her presence while he is recuperating. He even asks her cousin later if she was 'playing Florence Nightingale' in hopes of getting a marriage proposal.
{The Marquess Wins a Wife by Aydra Richards} - I realised it may be the opposite - he is actually very obnoxious and she probably wants to strangle him because he throws tantrums - but she still looks after him and even chooses to forgo her own food for him. She has a habit of picking up 'strays', according to another but the feelings develop after he is recovered and deliberately working off his debt to the family.
I also did not include {Devil in Winter by Lisa Kleypas} because that is much later in their relationship and her feelings for him had already developed. It probably had a reverse effect with HIM falling badly in love with her; this is for the nursing party to fall for the patient.