Can not log in as administrator using screen sharing

Computers involved:

-Computer A running Mac OS 10.7.5 with two user profiles, "administrator" and "User B"

-Computer B running Mac OS 10.8.2 with one user profile, "User B"

-Both on the same network

What I want to do:

-I want to control Computer A, logged in as "adminstrator", from Computer B without touching Computer A

I thought Screen Sharing was the way to go, but I hit an obstacle:

Screen Sharing-settings on Computer A:

-Screen Sharing: On

-Allow only access for these users: "administrator" and "User B"

What I have tried:

-No one logged in to Computer A

-Click on Computer A in Finder on Computer B

-Click "Share screen"

-Log in-screen appears

-Enter "administrator" and password for the user "adminstrator"

What happens when i try this:

-Dialog appears with two options: 1. Share screen 2. Log in as "User B"

I dont want to log in as "User B". And if choose "Share screen" I have to go on Computer A again to click accept the share screen request, which defeats the purpose of logging in remotely.

Can anybody help me?

PS:

-Using screen sharing from Computer B while "adminstrator" is logged in on Computer A works just fine, but it requires me to click accept on Computer A which, again, defeats my purpose

-Logging in as "User B" works. But I want to use a lot of the software set up on "administrator", plus I want to be able to control the music playback on Computer A via Computer B, which strangely did not work when i was logged in as "User B".