The highest priority is meal planning. Ideally, try out the recipe first to get a handle on it. If time is short, ask a trusted friend to help find something — the range here is more complicated than penne with marinara, but less tricky than pad thai. Consider something that looks impressive but is actually quite easy, like a roast chicken with vegetables.
You're not a great chef, so don't try to fake it when you tell your date you want to cook for her. Mention that you're no Batali but that you enjoy improving each time you do cook. She'll appreciate the effort, and you'll feel a sudden drop in pressure.
Find out about any allergies/eating restrictions ahead of time. It would be great to defy our gender stereotype of being inconsiderate.
Do any complicated prep work a half-hour before she's supposed to arrive (and really, do as much as you can).
Set the playlist early and have it playing when she gets there. The less you have to think about, the better.
Have snacks out for both of you — ex: olives, cheeses, baguette — so there's no rush to eat.
Don't insist on doing everything yourself. When she offers to help (which she will), don't make her sit there twiddling her thumbs while you're pacing around stress-sweating. Have something in mind she can help with, because beyond being helpful, it's also significantly more fun to partake together than for the other person to just watch.
Use "taste tests" to mask your utter uncertainty. If you start to lose confidence once you're in the trenches, ask her to taste the sauce or risotto as a means of soliciting help without raising suspicion. If the taste is off-course, she'll likely have a suggestion for how to correct it — and this is much better than waiting until everything's finished.
This may seem like overkill, but the easiest mistake a non-chef can make when trying to have a conversation is losing track of cooking times. Run through the order of things beforehand, and if need be, write it down.
If the meal does get messed up irreparably, consider two pieces of advice: First, accepting failure with grace is a chance to show character, and second, if you're in good supply of wine (which you should be), the date is by no means over. Make a few self-deprecating jokes, put in a call to the nearest takeout place, and crack open another bottle.