I'm more or less canonblind to Bloodborne as well, but I feel exactly the same! From the few gifsets I've seen of the Doll, she seems like someone Mato would be majorly fond of.

Mato may very well try to hide from her at first thinking that she's another nightmare toy, but I think after some careful observation she'd realize her mistake and try to call out to her! Whatever ends up happening, I'm sure it'll be the start of the most ridiculously adorable kind of CR.