A 26" wheel bike with a small frame should be ok for someone of that height; my 80s peugeot road bike was originally my sisters' (also 4'11" and she happily toured it around the Pennine hills at the time on 700c wheels, admittedly with the saddle on it's lowest).

The other thing about smaller riders to factor in to the equation is to make sure that the 'cockpit' [i.e. the length between the tip of the saddle and the bars] is small enough to be comfortable - as a petite rider will likely have shorter arms in proportion to their height.

You didn't mention whether your query pertains to folding or non-folding bikes; I think a 24" or 20" folder might be better than a 26" as they are designed out of the box to be suitable for many differing sizes of rider and the low-stepthrough of folding frames is also appealing to smaller riders. If in fact you're thinking of a more road-bike kind of thing there are three main options for smaller wheels - including getting a junior framed road bike, one of the increasing amount of non-folding 'mini bikes' in the west like the Dahon Smoothhound or Hammerhead, or thirdly looking in a specialist petite bike by the manufacturer 'Terry Bicycles' who specialise in custom road bikes with a smaller cockpit and small front wheel that optimises the geometry for smaller riders.