Let's see, I've lost 6.5#+ in a week focusing explicitly on diet, and based on my workout last night, no lost strength.
Trying to lose weight purely from working out will disappoint you, I've done that for two years. I finally started paying attention to what I eat, modified a little bit of it, and the inches are coming off. So, it's your choice, but diet>working out.
I think the average rule of thumb for running is very apparent: 1 mile of running = 100 calories. That means 35 miles = 1# worth of calories. 15# = 52,500 calories, or 525 miles run.
Now, we're midmonth July, let's assume that the wedding is mid Oct., or 13 weeks from now. You'll need to clock 40.3 miles per week in order to lose 15 pounds by running. Or average 5.75 miles ran per day without increasing your current food intake. However, my ortho claims that you can lose 1400 calories per hour from "properly" using an elliptical - so 15 pounds is just 37.5 hours on that elliptical. Sadly, he didn't delve too deep into what "properly" meant, but I know he was describing a blistering pace as they determined that by experimenting on airborne qualified soldiers.
ETA - read a little further down, looks like you have a good eating habit, sounds like you need to get a little more serious with it, that's all, I wouldn't change your workout by much, except just up the intensity in all of it.