Peter comes into her life. Peter latches on and depends on her for not only a habitat, but surely for food and 'warmth' as well.

This is reminiscent of how a Tic operates.

Also, Peter eventually 'burrows' his way into her life and 'head' and begins laying his crazy little ideas (eggs) all over the place, they then multiply and take over until there is so little of the original host left, she is unable to resist his craziness any longer.

It may be interesting to look at the film as a true horror film, but in which the threat is the titular character or "BUG" (Peter) who actually seeks out, latches onto, and systematically destroys its host.

Just a thought - Peter is the Bug