The model was killed by the paralympian on Valentine's Day 2013. Pistorius denies a charge of premeditated murder.
A number of WhatsApp messages from Steenkamp to Pistorius were read out inside Pretoria's High Court on day 14 of the murder trial, suggesting that the couple were involved in a tempestuous relationship.
"You have picked on me excessively ... I do everything to make you happy and you do everything to throw tantrums," read one message from January 27, 2013. "I'm scared of you sometimes and how you snap at me and of how you will react to me.
"You make me happy 90% of the time and I think we are amazing together ... but I am not some other bitch ... trying to kill your vibe ... I'm the girl who fell in love with you but I'm also the girl who gets side-stepped when you are in a shit mood ... I get snapped at and told my accent and voices are annoying."
One exchange saw Steenkamp establish that she was not flirting with another man when the pair were at a party together.
"I was not flirting with anyone today," she wrote. "I feel sick that you suggested it ... I am terribly disappointed how the day ended."
Pistorius responded: "I want to talk to you. I want to sort this out. I don't want to have anything less than amazing for you and I'm sorry for the things I saw without thinking and for taking offence to some of your actions.
"I was upset that you just left me after we got food to go talk to a guy and I was standing right behind you watching you touch his arm and ignore me, and when I spoke up you introduced me which you could've done but when I left you just kept on chatting to him when clearly I was upset."
The trial continues.