Hi there.
Great looking Pulchra.
And yes it is almost full grown. Some of my pulchras have reached just over 12", but most are at 10-11".
As for the pictures with flash, If you are using a DSLR, or if your camera has manual options, turn tank lights on, bump your camera ISO up to 800(ish), set a shutter speed of around 1/40 and f.stop to f-1.8 - f-3.5 and you should get nicely sharp(ish) picture retaining all the blue coloring.
Here is one of my Pulchras shot in this way:
The pictured Pulchra is at about 12".