Spike - He gets jealous easily and feels emotions strongly.
Buffy - Buffy is always busy with slaying and you also worry about her getting hurt.
Willow - Willow uses magic a lot and it worries you slightly because you don't want her getting hurt or addicted to it.
Xander - He is over-protective and can get jealous. He also has some commitment issues.
Tara - Tara hates talking to new people which can be a little frustrating when you want to introduce her to your friends and family.
Anya - She's brutally honest and she finds it challenging to understand your feelings sometimes.