I dont believe that Tony or any of his crew had anything to do with her death, but rather, the implication being that Tony takes a perverse satisfaction in paying back the loan he believed Hesh had being anxious for.

I believe Hesh is insulted by Tony's presumption that the money would still be relevent or priority to him at a time like this (i.e - his girlfriends death) However, he wisely bites his tongue and quietly accepts.

Tony leaves, apologetic enough for her death, but still with an air of satisfaction, a sorta "there's your precious money" sorta thing.

Remember, where Hesh was becoming anxious over Tony's extending loan because he figured Tony could easily wipe the debt by killing him rather then just stiffing him and facing recourse, Tony, for his part, was becoming annoyed with what he interprets as Heshie's nagging persistance.