The parameters of your girlfriend would matter depending on the ratio of 'space' occupying, but let's ignore that for now.

I would put a cord or something around it to minimize the space; air needs to be warmed up too. You should try to tie it in such a way, that you have on one side a 'triple' layer (half of the bag bent, so something like this

/--------------\    Top
|     You      |
| /------------/
| \------------\ 
\--------------/   Bottom

<-----Width---->

instead of the normal situation

/----------------------------\  Top
-    You          Girlfriend |
\----------------------------/  Bottom

<------------Width----------->

If you have a thick (air) layer under you, you can keep the three layers of the sleeping bag on top of you, if you have a thin layer under you, since most cold is going through the ground, put the three layers of the sleeping bag underneath you (like in the picture).

Also you can fill the sleeping bag with clothes (they will be warm in the morning), water or other drink, and even your shoes (put them in a plastic bag).

The parameters of your girlfriend would matter depending on the ratio of 'space' occupying, but let's ignore that for now.

I would put a cord or something around it to minimize the space; air needs to be warmed up too. You should try to tie it in such a way, that you have on one side a 'triple' layer (half of the bag bent, so something like this

/--------------\    Top
|     You      |
| /------------/
| \------------\ 
\--------------/   Bottom

<-----Width---->

instead of the normal situation

/----------------------------\  Top
-       You           GF     |  GF = Girlfriend
\----------------------------/  Bottom

<------------Width----------->

If you have a thick (air) layer under you, you can keep the three layers of the sleeping bag on top of you, if you have a thin layer under you, since most cold is going through the ground, put the three layers of the sleeping bag underneath you (like in the picture).

Also you can fill the sleeping bag with clothes (they will be warm in the morning), water or other drink, and even your shoes (put them in a plastic bag).

The parameters of your girlfriend would matter depending on the ratio of 'space' occupying, but let's ignore that for now.

I would put a cord or something around it to minimize the space; air needs to be warmed up too. You should try to tie it in such a way, that you have on one side a 'triple' layer (half of the bag bent, so something like this

----------------
    Yourself 
/--------------\
|     You      |
| /------------/
| \------------\ 
\--------------/

instead of the normal situation

/----------------------------\
-    You          Girlfriend |
\----------------------------/

If you have a thick (air) layer under you, you can keep the three layers of the sleeping bag on top of you, if you have a thin layer under you, since most cold is going through the ground, put the three layers of the sleeping bag underneath you (like in the picture).

Also you can fill the sleeping bag with clothes (they will be warm in the morning), water or other drink, and even your shoes (put them in a plastic bag).

The parameters of your girlfriend would matter depending on the ratio of 'space' occupying, but let's ignore that for now.

I would put a cord or something around it to minimize the space; air needs to be warmed up too. You should try to tie it in such a way, that you have on one side a 'triple' layer (half of the bag bent, so something like this

/--------------\    Top
|     You      |
| /------------/
| \------------\ 
\--------------/   Bottom

<-----Width---->

instead of the normal situation

/----------------------------\  Top
-    You          Girlfriend |
\----------------------------/  Bottom

<------------Width----------->

If you have a thick (air) layer under you, you can keep the three layers of the sleeping bag on top of you, if you have a thin layer under you, since most cold is going through the ground, put the three layers of the sleeping bag underneath you (like in the picture).

Also you can fill the sleeping bag with clothes (they will be warm in the morning), water or other drink, and even your shoes (put them in a plastic bag).