Cass likes to think of herself as a welcoming, accepting sort of person. She tries to be. And in situations like this, that gets tested. You're new to the Family - and you're the child of the Joker. Well... She knows a thing or two about bad parents. That doesn't make you a bad person.
She can tell herself that. She can still see that this has been... hard. For the family. Bruce hides it best, but she's seen the way he tenses when you laugh. Everyone is uncomfortable with you. Jason is the worst. Hard to blame him, but still. Cass? Well... she's had fewer direct dealings with the clown than some of the family. She doesn't hold it against you, and it's not that you make her nervous, exactly. It's just...
You're hard to read. Okay? Very hard to read. Your mannerisms, postures, body language. Your moods don't match your body language, your mannerisms and movements are unpredictable. You are hard to read. ...Like your father. And Cass doesn't want to think of you that way, but it's hard not to, sometimes.
And it's not that she's even trying to read you, specifically. It isn't a lack of trust, so much as just... how she functions, operates, exists. But being unable to read you the way she so naturally can most others does make some part of her feel uneasy, and that could lead to a lack of trust, and...
She's the problem here. And she doesn't want to be. And sometimes? Sometimes she thinks she can read you, better than she thinks. Sometimes she sees little moments, and sometimes you seem... sad. Lonely. Scared. But maybe she's projecting? She remembers how she felt, when she first came to Gotham. She can only imagine the things you've been through. ...She's seen some of your scars. She has her own.
On some level? Cass imagines a world where the two of you could be... friends. But you're just so hard to read, and... well. She's going to just have to try and get over that, isn't she?
"Oh. Hello," she offers, pausing as she steps into the room to find you already there. Mood? Indeterminate. Sigh.