Preeclampsia after birth??

A friend of mine just had her baby and I messaged her asking how she was and she said she’s back at the hospital bc her blood pressure got super high and her liver was getting messed up so she was in pain and she went to the hospital and they told her she developed preeclampsia after birth? She was extremely swollen before birth so is it possible it went undetected? I don’t think her blood pressure was high before