I`m in dilemma right now.......

I have a gf.....we dated about 8 month now..... she`s nice. but the only thing really annoy me is she`s always sulking for a small reason ( for example text her late, not anwering her call ). sometimes for no reason at all...I knew it`s normal for a girl to sulking or merajuk but sometimes it nearly reach my boiling point. when she`s sulking she will silent for about a week no matter how many times I call or txt her.........when she`s finally respond ( many times when I have to start it first ) she will act normal like nothing happen........when I ask her what happen she`s not answering and quickly change the subject...........

there`s a time when I reveal my frustration about her attitude she became emotional and start saying lame things ( for example you`re too good for me ) and start threatening to end our relationship.....and what can I do is just silent, comfort and persuade her to continue our relatonship.........

she have a bf before this but she`s got dumped.....i began to think i maybe it has something to do with her always sulking attitude.........

I love her.......but now I became tired........ shoud I give her a chance. or should i break up with her and move on.........