Deadly, dangerous, deranged, devoted
Bellatrix is one of the two females in Lord Voldemort's inner circle and she's very proud of that fact. She is arrogant and highly ambitious, hoping to become the Dark Lord's right hand woman. In that resepct, she is very competitive and to those she sees as threats, she is spiteful and mistrusting.
Bella is a law unto herself, she does what she wants, when she wants and how she wants; the only one who can truly control her being the Dark Lord himself. She is overbearing and can be very intimidating when she wants to be. Her temper is highly volatile and it takes very little to provoke it.
Bella is not an overly friendly person; she either likes you, loathes you or wants to completely and utterly destroy you. While she can be a flirt and a temptress when she has little else to do but find ways of curing her boredom and 'getting one over on Rodolphus' and so any 'lovers' would most likely be flings. She would seduce a man - a pureblood man mind you, nothing less (at least to her knowledge) - and afterwards treat him like dirt because she's got what she wants. She would have a whole horde of enemies as she doesn't pretend to be friendly unless she wants something from you.