separation anxiety behavior
Does separation anxiety happen at night when baby has fallen asleep?

My 8th month baby tends to cry in middle of night several times and we have to rock her then she fallen asleep again. Is it normal or maybe other reasons on her behaviour?

It can.

Also, your baby might have a sleep association. Do you rock her to sleep before bed ? If so, then remember that she needs whatever she has before bedtime to fall back asleep if she wakes at night (pacifier, bottle, rocking etc)