I started out with 4 blue acaras, and an oscar to keep them in line.. the Acaras are tougher than they seem! they keep the Oscar (which is 3 times the size of the acara) in line, and i now have to many acara to count, even after i've twice traded some in for supplies.
Anyways.. i would say that yours is female. Males generally, have more pointed fins, which, over time, grow to overlap the tailfin. As for colouration, males are generally bighter overall, and more showy, female seem to be darker, but, show more contrast between the vertical stripes when in breeding mood, with very distinct white/black stripes. the males stripes are more royal blue/sky blue colouration. Wait a few days and observe to see what happens, until the fish decide who is the "boss" of the tank. Being newly introduced, she is effectively the bottom of the pecking order and will not show much colouration, until she settles down, and figures out how she sits in the order of things. When they all know who's who, they will start to show full colours.
As for cichlid tank mates, as long as you have sufficient objects (caves, bits of bogwood, large plants), so then fish can easily identify teritories and boundries, and you choose one of a compatible size, then you shouldn't face much trouble from any choice. I've read and heard that convicts, or salvinis would be bad, but i had no experience with either so, not really sure, but they have a bad rep from someplace.