I think you will be fine taking the normal precautions.

I walk home most nights from Broad and Walnut.

So I walk:

Down Walnut or Sansom
Head North on 3rd
East on Spring Garden
North on 2nd up to Girard

I am a single female (early 30s) and no one has ever bothered me. I prefer taking 3rd North from Old City and not 2nd because it seems to be a little busier and safer but that's just me. Again, taking the normal precautions you should be fine.