 Although initially happy in her relationship with Jackson , Lexie is distraught when she learns that Mark has begun a relationship with a woman named Julia . At a charity softball match , her jealousy gets the better of her , resulting in her throwing a ball at Julia . Sensing that Lexie is still in love with Mark , Jackson calls off their relationship . Lexie begins working with Derek 's service and becomes increasingly proficient in neurosurgery , helping Derek with a set of " hopeless cases " - high risk surgeries for patients who had otherwise run out of options . During a surgery , Derek is called away on an emergency , leaving Lexie and Meredith to carry out the procedure on their own . Though Derek had instructed them to merely reduce the patient 's brain tumour , Meredith allows Lexie to remove it completely . The sisters celebrate the successful surgery , but when the patient wakes up , Lexie is devastated to discover that the patient suffered severe brain damage , losing the ability to speak . Alex , Jackson and April Kepner ( Sarah Drew ) move out of Meredith 's house without inviting Lexie to join them , and with Derek and Meredith settling down with baby Zola , Lexie begins to feel increasingly lonely and isolated . After being left babysitting Zola on Valentine 's Day , she decides to try to salvage her relationship with Mark . However , after plucking up the courage to visit his apartment , she finds Mark studying with Jackson and loses her nerve , instead claiming that she was visiting to set up a play date for Zola and Sofia . When Mark confides in Derek that he and Julia have been discussing having a baby , Derek warns Lexie not to miss her chance again , resulting in her professing her love to a shell @-@ shocked Mark , who merely thanks her for her candour . He later confesses to Derek that he feels the same way , but is unsure about how to go about things . Days later , Lexie is named as part of a team of surgeons that will be sent to Boise to separate conjoined twins , along with Mark , Meredith , Derek , Cristina and Arizona Robbins ( Jessica Capshaw ) ; however , while flying to their destination , the doctors ' plane crashes in the wilderness . Lexie is crushed under debris from the plane , but manages to alert Mark and Cristina to help her . The pair try in vain to free Lexie , who realises that she is suffering from a hemothorax and is unlikely to survive . While Cristina tries to find Meredith , Mark takes Lexie by the hand and professes his love for her , telling her that they were " meant to be " . While fantasizing about the future that she and Mark could have had together , Lexie succumbs to her injuries , and dies moments before Meredith arrives . The remaining doctors are left in the woods waiting for rescue , with Mark refusing to let go of Lexie 's hand . 
