What Causes Dark Bruising On Arms And Legs With Small Spots In It?

My friend has unexpalined dark/black bruising on her arms, legs and sometimes stomach. WHen I mean dark they are severly black and purple in colour and takes weeks to dissapear. Some have small spots resting on the bruise itself. I have advise her to go for blood test fom her G.P, but what suggestions could this be? She is age 40, smokes and slightly inemic (exuse the spelling)