My 2 cents,I think it would be regrettable to cut it to 2 in.If you must cut it,I'd go about 1/4 in longer than the ejector rod housing.
Before you do that.I highly regard single actions.I have a single action Ruger on my "buy next" list.
But if you feel a need for her to have a carry piece(entirely reasonable) I suggest not going too far in the "make do" direction.Its serious business.
Your Single Six is tradeable.
There are a lot of smaller frame .38 spl's available.Midrange target wadcutters hardly recoil at all and do not make much noise.LadySmith?Charter?There are some new Rugers,I have not been following.
If you choose to go single action,Cimmaron offers a 3 in bbl birdshead grip small frame in .38spl.Ifs a traditional colt type,so you only load 5.The larger frame in .44spl is the Thunderer,this is a small frame,Lightning.,They are sweet!!
But,I'll say again,there are safer and more practical choices ..32 H+R,imo,would be another mild choice I would prefer to a 2 in 22 mag.
http://cimarron-firearms.com/Specialty/Lightning.htm