Fight and kill the guards at the gate (this will not fail your quest).
Cynthia Hammers is also the name of a retired adult film performer active in the late 1990s.
Cynthia Eid is a world-renowned master metalsmith and author. Her advice on purchasing and using forming hammers is legendary in the jewelry-making community. cynthia hammers
There is no widely known official guide or entity named "Cynthia Hammers." It is highly likely that your request refers to one of a few distinct topics:
Avoid purchasing cool-looking, expensive hammers before you know what they do. Fight and kill the guards at the gate
Buy hammers similar to what your workshop instructor recommends so you know they are useful.
Cast an invisibility spell on her and walk out, or pick/break an outer wall window and climb through. Her advice on purchasing and using forming hammers
Once free, escorting her safely to the camp or back to Ashbury completes the quest and awards alignment points.