The only alternative I know by train is Birmingham. This isn't normally valid on a Stoke-Lichfield City ticket, but is valid on the slightly dearer Kidsgrove-Lichfield City tickets (which you can use for a journey between Stoke and Lichfield).
You could ask London Midland or Crosscountry about your mother taking the longer route. As Lichfield Trent Valley is a lot harder to get around, they're likely to be fine about it with either ticket.