Vriska likes Murasa, in as much as she likes anyone she knows. More than she likes most other people so that's something. Largely because Murasa actually seems interested in what she can do and stuff, and because they can talk without excessive fawning or arguing which is...unusual. Also because they can bond over how frustrating Eiki is.

But yes, I agree with your assessment, casual friends but that in itself is a pretty big deal for her.