Dealing with "accidents"--questions

So Blueberry potty trained very nicely and easily when she was a little over two years old. However, at three and a half, we have been dealing with a number of accidents lately--which she almost never had before this. Primarily, it seems to be that she's just so busy playing that she forgets or doesn't think about needing to use the restroom until to late.

But of course there's the questions that go with it.

How does one best respond to these instances?

I mean, the first few, we just dealt and moved on, no big deal. But it keeps happening.

I don't want to make a huge deal about it because I don't want it to become some kind of complex thing. But at the same time, going through several pairs of panties in a day is really hard on the laundry, never mind the mess, etc.

Of course I "should" remind her frequently, and I try to. But when I'm bouncing around from kid to kid in our crazy, current group of nine, it's easy to forget (insert large load of mom-guilt here).

Or is this simply a phase she will grow out of, and I need to just not worry about it, keep reminding her to go potty when I think about it, reinforce going right away and not waiting, and just let it go?