50NL - Small Flush

[Kwakubah]

PokerStars No-Limit Hold'em, $0.50 BB (8 handed) internettexasholdem.com

saw flop|<font color="#C00000">saw showdown</font>

<font color="#C00000">MP1 ($38.65)</font>
MP2 ($67.95)
CO ($26.25)
Button ($49.25)
SB ($49.50)
BB ($92.15)
<font color="#C00000">Hero ($45.85)</font>
UTG+1 ($47.60)

Preflop: Hero is UTG with 5[img]/images/graemlins/diamond.gif[/img], 6[img]/images/graemlins/diamond.gif[/img].
Hero calls $0.50, UTG+1 calls $0.50, MP1 calls $0.50, <font color="#666666">3 folds</font>, SB completes, BB checks.

Flop: ($2.50) Q[img]/images/graemlins/spade.gif[/img], A[img]/images/graemlins/diamond.gif[/img], 3[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(5 players)</font>
SB checks, BB checks, Hero checks, UTG+1 checks, <font color="#CC3333">MP1 bets $0.5</font>, SB folds, BB folds, Hero calls $0.50, UTG+1 folds.

Turn: ($3.50) 4[img]/images/graemlins/diamond.gif[/img] <font color="#0000FF">(2 players)</font>
Hero checks, <font color="#CC3333">MP1 bets $1.5</font>, Hero calls $1.50.

River: ($6.50) 7[img]/images/graemlins/heart.gif[/img] <font color="#0000FF">(2 players)</font>
<font color="#CC3333">Hero bets $4</font>, <font color="#CC3333">MP1 raises to $8</font>, Hero....

Is this an instant reraise? I've recently had a couple small flushes beat by bigger flushes so I'm feeling a bit tentative.