E.S.
These are some of my favorite authors. Jeffrey Deaver, Michael Connelly and LIsa Gardner. They each have a series (or two) so you may want to get early books so if she gets into it she can continue to read the rest of the series. If she hasn't read the Stephanie Plum series by Janet Evanovich, the early ones are laugh out loud funny (and I don't say that about much) and have a mystery story to them.