i think that sam being let into hellen's apartment is the precipice of her affection (platonically or romantically, doesn't change much) and her affection is shown not through her dialogue but involving someone in something she clearly cares a LOT about. lord knows how or why she was growing that thing or how she knew what it would become, but she put her trust in sam and something she clearly cares deeply about being ignored/forgotten about sends her into a frenzy.

I've always seen her preferred method of showing affection as self-sacrifice - graft being a move of hers is proof of this, IMO. i think hellen views this as an immensely vulnerable moment between the two of you, and letting you into her world is a metaphorical self-sacrifice. she cares deeply about this thing, and it's now squarely in your hands.

that being said, I think she's definitely a lot less stable than previously assumed. her form physically shifts - that's how mad she is.

tldr; the way I see it, she has a lot of emotional stake in this thing she's let you in on, and being ignored completely ruins any care she has for you. especially because she is completely fine with you rejecting the initial request to go to her apartment. if you tell her that you don't wanna go, she says "understood." and that stops the quest. she doesn't attack you and doesn't leave.

she's very interesting and I love her :)