That depends on her preferred dress, like pants or dresses? Does she do both?
It's better to stay away from off-the-body carry, like a purse. May be the first thing a bad guy would grab, before she noticed him. Then no gun and she's helpless.
The Ruger Store has a selection of LCR holsters, and Ruger's website has a compatibility list for holsters. You could also search shooter's supplies like Midway USA for "LCR holster".
I have a Galco Stinger, from Ruger Store, but now they don't show it. It's an open top, on the belt holster. Also a Galco Stow-N-Go for inside the waistband, and a DeSantis Nemesis for pocket carry.
Some holsters made for S&W's J-frame snub nose revolvers will work, but most don't, as the LCR trigger guard is larger. I would not trust buying one unless you could physically try a LCR in it first, in person.
Others will chime in with more specific recommendations, I'm sure.