Does shady spectacles make unity mighty and proc fiora?

Yes — if you copy a unit with 5+ Might, the equipped unit becomes Mighty, and that transition procs Fiora, Worthy.

Shady Spectacles copies the target's printed Might (Rule 477.1.b.1.a; FAQ #12291), so equipping a small unit and copying a 12-Might Baron leaves you with a 12-Might Baron copy — which is Mighty (Rule 708). Since that unit was already in play and its Might crossed from below 5 to 5+, that's a "becomes Mighty" moment (Rule 709), so Fiora, Worthy's "When a unit you control becomes Mighty, you may pay [C] to ready it" triggers. This is the same kind of on-board crossing that fires when you move an existing unit onto Trifarian War Camp — not the "enters already Mighty" case, which never triggers.

Caveats: no trigger if the equipped unit was already Mighty (no status change), and you only inherit the target's printed Might — copying a unit that's only Mighty from a temporary buff or gear leaves your copy below 5. And if you meant Fiora, Victorious, copying her won't help: she's printed at 4 Might, so the copy isn't Mighty and gets no Deflect/Ganking/Shield unless something else pushes it to 5+.