I think at some point the dwarfs have to be liberated because they are on Snow and Charming’s war counsel and like you said they were with Snow at her coffin.
Though i also think that the house that they show Grumpy sneaking out of to go to Nova seemed like the same house that Snow was living in with the dwarfs at the end of Ep 10 when they show that she has taken the potion and lost her memories. That makes me wonder when the liberation takes place and that maybe it happens later on possibly while they are trying to help Snow after she loses her memories or maybe after the glass coffin incident when Snow wakes up the dwarfs decide to go with her and help her. I am not sure. They need to give us more details.