Should I add more wort or leave it be?

Doing my first high grav brew tonight, and so I also made my first ever yeast starter last night. English Old Ale with a target OG of 77. I'm afraid I did too little too late. Last night I boiled 1/2 cup DME in 2 cups of water, cooled, added a vial of WLP002 , covered with tin foil, and left to lose at poker. I'm probably 15 hours out from pitching tonight. Should I quickly boil another 1/2 cup DME in 2 cups water, cool it, and add it to my growler, or just let it go at this point? I figure most likely the yeast won't really have time to eat an additional helping of maltose by tonight anyway.

You should be fine, but the yeast situation isn't optimal. It will likely ferment properly though. I would just make sure you get a really good aeration on the wort before you pitch.

maybe i should stop by the LHBS on the way home from work and grab a second vial and just dump that vial along with the starter into my beer tonight. Or maybe I should sacrifice my sunday to brewing and kick up the DME dose tonight...

I'd just RDWHAHB

you could always wait and pitch it a day or so later. I've done this plenty of times as long as everything is sealed up and sanitary you have nothing to worry about