bad push?

No read. i kicked myself because a thinking player doesn't usually call that sort of bet with a flush on a paired board. i guess i view it as everyone is a donk until proven otherwise. horrible horrible slump at the moment

------HAND 8------
Game #2688709854: Hold'em NL ($0.25/$0.50) - 2006/06/14 - 14:10:00 (UK)
Table "Pantomime" Seat 2 is the button.
Seat 1: Rebellis ($21.75 in chips)
Seat 2: Simba72 ($52.70 in chips)
Seat 3: Smiffy44 ($46.75 in chips)
Seat 4: spolingen ($50 in chips)
Seat 5: zenpoker ($37.10 in chips)
Seat 6: anonimous ($63.50 in chips)
Seat 7: Judgment ($40.25 in chips)
Seat 8: qqqcutie ($40.35 in chips)
Seat 9: aikman13 ($107.20 in chips)
Seat 10: mueller ($47.75 in chips)
Smiffy44: posts small blind $0.25
spolingen: posts big blind $0.50
----- HOLE CARDS -----
dealt to Smiffy44 [7s 6s]
zenpoker: calls $0.50
anonimous: folds
Judgment: folds
qqqcutie: folds
aikman13: calls $0.50
mueller: calls $0.50
Rebellis: folds
Simba72: folds
Smiffy44: calls $0.25
spolingen: checks
----- FLOP ----- [8s 4d 4s]
Smiffy44: checks
spolingen: bets $1
zenpoker: folds
aikman13: folds
zenpoker leaves the table
mueller: calls $1
Smiffy44: calls $1
----- TURN ----- [8s 4d 4s][5s]
Smiffy44: bets $4
spolingen: folds
mueller: calls $4
----- RIVER ----- [8s 4d 4s 5s][7h]
Smiffy44: bets $41.25 and is all-in
paquinnn joins the table at seat #5
mueller: folds
Returned uncalled bets $41.25 to Smiffy44
Smiffy44: doesn't show hand
Smiffy44 collects $12.85 from Main pot
----- SUMMARY -----
Total pot $13.50 Main pot $12.85 Rake $0.65
Board [8s 4d 4s 5s 7h]
Seat 1: Rebellis folded before Flop (didn't bet)
Seat 2: Simba72 (button) folded before Flop (didn't bet)
Seat 3: Smiffy44 (small blind) collected $12.85
Seat 4: spolingen (big blind) folded on the Turn
Seat 6: anonimous folded before Flop (didn't bet)
Seat 7: Judgment folded before Flop (didn't bet)
Seat 8: qqqcutie folded before Flop (didn't bet)
Seat 9: aikman13 folded on the Flop
Seat 10: mueller folded on the River

On the river with the nuts it really comes down to a math problem. How often do you think the villain will call this bet? What about a PSB? What about a 1/2 pot bet? It is hard to say what the best play here is without a read on what the villain will call. Readless I would probably just bet $10ish on the river, your line seems a lot like a flush [check/call with draw, lead turn when flush hits] by pushing you are really only getting called by a full house or ace-high, maybe king-high flushes neither of which seem all that likely, but I guess are still possible.

There is a chapter in NLHE:TAP about how much to bet on the river with the nuts, its good reading, you should check that out.