Very clever film. Most people dont seem to understand the ending...
Spoiler alert.
If you know about psychology, this film isnt about an alien invasion at all. It's about how guilt and shame can lead to self loathing and birth inner demons. And they will keep ruining your life until you learn to show compassion and acceptance to yourself and heal those inner wounds. Only when she shows her inner child some compassion and love, do the 'aliens' (inner demons) leave her alone...