I am very sorry to see your struggling oleander following that rather severe wintry spell.
Sadly I am wondering if it is going to suffer the same fate as many of our mature palms..............out of all the some 12 we have ...........all doing very well,we have lost 4 already and may well lose another two..............so heartbreaking.
The one in the picture, such a beautiful specimen has lost several legs since this picture was taken.
Though with palms there is every likelyhood they will again regrow.
I do not know whether this could apply to your poorly plant Petra...........but I hope it does survive as they are so pretty when in bloom.