The first thing I would do is read age appropriate books to her. When you read, discuss what is happening. Look at the pictures, talk about what the characters are wearing, ask her what are they doing, why are they doing this, why do you think they are doing this, what do you think will happen next? If she cannot answer, then model answers for her eg. answer the questions yourself, then ask her an easier question which you know she will be able to answer so she feels successful. This will help with the acquisition of language. Likewise, singing songs such as nursery rhymes will help with language development.
The second thing would be to do as you are doing and simply model the language. If she wants a biscuit and just says 'biscuit', you say 'Would you like a biscuit?'' Wait for her reply. If she says "yes", you could say "Yes, I would like a biscuit" which will give her the language and provide her with a model. If she takes you to what she wants just use that as an opportunity to model language and extend her vocabulary. It is okay for her to copy you, she is learning.
The third thing would be to talk with her about her day. For instance, at dinner time, you could make a habit of talking with her about her day to get her thinking about what she has done that day. At first you could ask her and wait for her response, if she doesn't know, then you could tell her what she has done and ask her questions about it such as if she enjoyed it or not etc.
The fourth thing is to deliberately do the wrong thing. If she hands you the remote wanting you to change the channel, you could turn it off and then she has to ask you to turn it back on and which channel/show. You could continue to make "mistakes" depending on whether she is okay with it or stop if she is getting frustrated.
A fifth idea is an activity called manding. Your daughter would tell you what you have to do. For instance, direct you from one room in the house to another. She would say 'walk to the door, turn, walk to...' and you would expect increasingly more complex language, such as 'stand up, turn around, walk to the bedroom door, turn right, walk to the lounge room door, turn left, walk into the room...'. Any scenario you can use, getting food she wants, going outside for a walk, household chores etc. You could also make "mistakes" during this and she has to correct you. Make it fun!
(Is your daughter shy around others and is that why she doesn't answer?)
Hope these suggestions help!