Not even messed up really. This all happens in the brain.
Regardless of any discussion about ego and stuff the brain's first
job is keeping its owner safe, so whatever communcations
it's having with the wider world including other people it will always
divert attention to deal with a threat. The basic responses are well before
anything gets to conscious awareness.

So even in the presence of someone one claims to love, those
circuits will always be vigilant. Thus something that seems a threat
elicited by a loved one/lover will trigger the threat responses. These
responses, once in conscious awareness (perhaps on the way to) can be
adjusted by other processes in higher centres.

It can also happen for (colloquially) "selfish" reasons. If one is pursuing some
kind of goal (we all do, many times a day) and someone interferes with
that, the threat response is triggered, no matter what the quality of the
"threat" anyway stopping us from doing what we individually have to. Again, higher
cortical processes can modify how we deal with it.

When an individual's continuing goals clash with those of another person - in
this case a beloved - and that person feels ostracised - both will experience
enough threat to become stress and organise their actions either to regain
the status quo or avoid the source of the threat.
That's when love and minds seem messed up.

Interesting, though, that love-attachment could be more like a drug than
many think. I was reading about this last night but want to check the
references when I get time. The author (Louis Cozolino*) claimed
some success "curing" attachment addiction by using therapies for
weaning people off physical drugs like alcohol.
.
* An author published by W.W.Norton.