
Even though the door is open to the garden you still have to accompany her out to the garden so you can praise and treat her when she toilets in the garden. You will also then know when she last went and so can gauge when you need to take her out again.
With regard to night time you may need to get up in the night to take her out and thus help prevent accidents indoors. I am not a huge fan of paper training myself as, to my way of thinking, it tells the puppy that it is okay to go indoors when what you are actually aiming for is for the puppy to learn it
doesn't go indoors. At some point you will stop using the paper and the pup has to learn all over again :) I know some people do use this method but it seems to be twice the amount of training to me.
Your puppy is still very young and is bound to have the odd accident. Never tell her off just clear it up, rinse with biological washing powder, and keep a constant watch for signs she needs to go out, such as circling and sniffing and whip her straight out into the garden.