Eventually/At last she lost her identity because of it.
lose oneself 一般是用于沉迷于.
自我的话一般用identity,也就是自己的身份表示.这种说法比较正宗.
Eventually/At last she lost her individual being because of it.
在这里 individual being是相当经典的表示.是罗素（诺贝尔文学奖获得者,哲学家,数学学家）在 How to grow old 一文中的表述方式