If your girlfriend is suddenly acting cold and distant, there may be Have you been acting too clingy (aka demanding too much of her time?).
One such way a relationship might change is when you feel your partner becoming somewhat distant. Sometimes relationships change, no matter how much we wish they wouldn't, so it's normal to feel a partner begin to pull away if you've been together for awhile and things haven't been the same. Anyone who's ever experienced this knows that it can be really scary, because knowing exactly what to do when your partner is acting distantwithout pushing them away even more, can definitely be a challenge.
Another aspect to consider when addressing a partner's change in behavior is how long you've been dating. Addressing these types of concerns with someone who you have a history with can be much less intimidating than bringing it up to someone you've just started seeing.
We all have things we're working on, so trying to address each other's shortcomings from a place of understanding is key.