Hmmm ... I was going to suggest the Audix OM series, especially for live stuff.   They make several models, might be worth trying out the ones your guys dont have, see if she likes them better.

Shure SM58 and be done with it.  takes a beating and keeps on tickin'.

ditto....SM58..it doesn't have a switch, i believe they make a model called the SM48 that does..but i could be wrong.

Oh yes I forgot to address the "On/Off" switch. Here's why SM58's DON'T have them. #1 Every time you add a contact point in an audio line (i.e an on/off switch or any other connector) you add the potential for NOISE! It can pick up RF or a whole myriad of other interferences, buzzes and hums!  #2 They break! and did I mention the noise? #3 every time you open and close that switch you create a huge POP and that CAN blow speakers. Not a good thing. If you want to talk off mic, put the thing on the stand and walk away from it, put your hand over it, hold it behind your back, whatever. Pro mics don't have on/off switches for those reasons! Don't get a kiddy mic! Get a pro mic. It doesn't HAVE to be a SM58 just cuz I said so. But I wouldn't buy one with an on/off switch for live applications unless you have a good sound man that can pull that mic channel out when your going to play with the on/off switch! LOL Is it just me or does anyone else get the fact that I don't like on/off switches on mics? LMAO!  

Thanks much for the help and suggestions!

We got together for a while on Monday night and I tried out an Audix OM 3.  I thought it was great (even made me sound good!) but my sister was sorta indifferent.  I have a buddy that can lone me a Shure Beta 58 to try out next week--should be able to make a decision after that.