I tought two ways for this:
1- Maybe changing the delay value to how long you want from registry works, try it (I was going to try but I couldn't wait at least 5001 second to test it.)
Start>Run>type "regedit">OK then browse for HKEY_CURRENT_USER/Software/Patchou/Messenger Plus! Live/your e-mail address/Preferences/PersoStatusRepeatDelay/(here set the delay 100000 for instance)
I hope someone who knows much about this correct me if it won't work.
2- Note that there is a tooltip on the auto-responder area, that is "You can create a sequence of multiple different messages by starting new lines with #." By making new lines by Ctrl+Enter there, you can insert consecutive commands which will be run locally, such as #/close so after your girlfriend takes your first response, if she sends again, her window will be closed (make sure you set the highest possible delay before setting this because a chat log file (if you keep) which is splitted into hundreds of sessions wouldn't be nice.) You could also use the /block command but I know it would be very offensive for your girlfriend
By the way, if there exist a /disableresponder command, everything would be nice.
* ahmetgns goes to General Talk forum and suggests it immediately 
/Done: [suggestion]/disableresponder command
/ 
