Honestly yeah you'd think that people would recognise the demon lords daughter. At the very least you'd think chika would since she fought with the reincarnated and all.
To be honest silkie probably considers herself to be a girl at this point considering how she's lived an entire second life as a woman so far and has no issues woth wearing a bikini. it's not even a thing where she's wearing a jacket or pareo with it. the only other thing she has is that towel around her shoulders. As for being in love with Freille, yeah I feel like she might be. Also lesbians do exist.
As for your last question, she wasn't trying to undress her she was trying to snatch the towel away since she wanted her to "show more skin". Interpret that however you will.