Digital multimeters vary widely in their ability to deal with AC voltage measurements. My Tektronix DM501 and DM502 both have compensated attenuators and they are specified at both 10KHz and 20KHz (±0.7% and ±1.6% respectively, as I recall) and says that it's useable to 100KHz, begin down only around 5%.
I've checked some of Flukes better handheld DMMs and found them to have very poor frequency response much over 1KHz. On the other hand, I've checked Simpson 260 analog VOMs and found them not too back up to around 100KHz. In fact, those "lousy analog meters" were actually more accurate at measuring 50KHz AC voltages than were any of the handheld multimeters that we had available.
Most handheld DMMs do not have compensated attenuators. The better bench DMMs do.
Dean