Didi always wanted a tatoo and this was a sketch she did of one that she would have liked to have had done. The recurrent themes of broken heart, blood and shards of glass are icons she uses a lot in her drawings.
This tatoo was intended to convey the brittleness of the heart and how easy it is for it to shatter, given enough unpleasant vibes and experiences. Those vibes and experiences are represented by the "incoming" black sharp and round objects at the top and sides of the heart. The round ones are supposed to represent "nice" experiences and the sharp ones unpleasant ones. It was Didi's experience of life by 1988 when she was 19 that life was mostly full of unpleasant experiences and vibes, hence there being more sharp and jagged icons than round ones, enough to shatter her heart into shards of glass.