How to set up a shared account in GnuCash?

[Jari Pääkkö]

Hi,

I recently opened a shared checking account with my girlfriend and I'm 
not quite sure how to set that up in GnuCash. The idea is that both of 
us deposit an equal amount of money every month to the shared account. 
We then use the shared account to pay for our common groceries, bills 
etc. However, when using the shared account, I would want to track my 
half of the expenses separate from hers. For example, if we buy 
groceries for $50 using the shared account, I would only want to track 
$25 as my expenses. I tried to do this in GnuCash, but I stumbled upon a 
couple of problems. Here's the account tree I tried to use:

-Assets
   -Current Assets
      -My Checking Account
      -Shared Checking Account
-Expenses
   -Groceries

Here's an example scenario:

-Assets
   -Current Assets
      -My Checking Account         $25
      -Shared Checking Account     $0
-Expenses
   -Groceries                      $0

Let's say that I transfer $25 from "My Checking Account" to "Shared 
Checking Account":

-Assets
   -Current Assets
      -My Checking Account        $0
      -Shared Checking Account    $25
-Expenses
   -Groceries                     $0

Now, my girlfriend transfers also $25 from her checking account to 
"Shared Checking Account":

-Assets
   -Current Assets
      -My Checking Account        $0
      -Shared Checking Account    $50
-Expenses
   -Groceries                     $0

How should I record this in GnuCash? As I see it, I should create an 
account representing my girlfriend's asset account and transfer the 
money from there. However, I'm not quite sure, if this is right.

Continuing the scenario, we buy groceries for $50 using the shared 
account. However, I only want to track my half of the expenses instead 
of the overall expenses. So, instead of putting $50 in 
Expenses:Groceries, I only want to put $25 in Expenses:Groceries:

-Assets
   -Current Assets
      -My Checking Account        $0
      -Shared Checking Account    $25
-Expenses
   -Groceries                     $25

However, now I should still somehow record my girlfriend's half of the 
expenses. How should I do this? One solution would be to create a new 
account representing my girlfriends expenses and put her half of the 
expenses there. Again, I'm not quite sure, if this is the right way to 
do this.

Am I completely on the wrong track here or how should I set up a shared 
account in GnuCash? Hopefully I stated my problem clear enough. Thanks 
in advance for any help!

Jari