The Hornets had a plethora of chances in the first half but couldn't put themselves in front at the break.
In an all-action second half, Bentley produced a super penalty save to deny Jerson Dos Santos. But the Hornets conceded another penalty moments later, and this time the 18-year-old couldn't keep out Ira Jackson's spot-kick.
A Joe Shelley own goal put Invicta 2-0 up before substitute Gary Charman halved the deficit. Horsham bombarded the Seasiders box with corners in the dying embers but couldn't snatch a point.
The result sees the Hornets drop to third. Local rivals Worthing leapfrogged the Hornets into second after a 2-1 home win over Margate.
Victory for Invicta sees them go three points clear at the top of the Premier Division.
Dominic Di Paola made two changes from Tuesday night's Sussex Senior Cup win at Littlehampton Town. Jack Brivio and Steve Metcalf replaced Alex Kelly and Taurean Roberts.
The Hornets were quick out the traps and bossed the opening ten minutes.
Kieron Pamment fired just past the post before Chris Smith spurned a gilt-edged chance.
Invicta keeper Henry Newcombe inexplicably gave the ball straight to the Horsham forward. Smith shimmied round Newcombe but somehow contrived to miss the target from a yard out.
And just five minutes later Newcombe's blushes were spared for a second time. The Seasiders stopper failed to catch the ball from a corner and the ball fell to Brivio in the box.
Brivio looked certain to score but a superb goal-line clearance from Alfie Paxman denied Horsham.
Folkestone had their first chance of the afternoon on 17 minutes. Jackson did well to fire off a shot but it was straight at Bentley.
Horsham did have the ball in the net just before the half-hour mark but the linesman ruled out Harvey Sparks' poked finish out for offside.
Jackson should have put Invicta ahead six minutes before the break. The Seasiders striker brilliantly broke the Hornets' offside trap.
The forward found himself one-one with Bentley but the young keeper made a terrific save to keep the game goalless at half-time.
And six minutes after the restart Bentley was Horsham's saviour once again. The hosts were awarded a spot-kick but Bentley repeated his Senior Cup shootout heroics to expertly save Dos Santos' penalty.
But Invicta were given a second opportunity to take the lead as they won another penalty on 65 minutes. This time Jackson took the spot-kick and he made no mistake from 12-yards.
The Seasiders began to control the game and came close to doubling their advantage. Josh Vincent produced a marvellous diving header but his attempt from a few yards out went wide.
Folkestone did make it 2-0 with 12 minutes to go after Shelley's own goal but the Hornets fought back.
Just two minutes after going two down substitute Charman powered a header into the net to cut the deficit.
Invicta almost restored their two goal lead with six minutes remaining. Kieron McCann's excellent effort took a deflection and crashed against the post.
Horsham won a succession of corners at the death but couldn't find that elusive equaliser as they suffered their second consecutive league defeat.
Horsham: Bentley, O'Sullivan, Sparks, Brivio, Shelley, Merchant (Dyett 66), Pamment (Goddard 80), Dawson, Smith (Charman 65), Harris, Metcalf. Unused: Karl.