To nice to my girlfriend?

ok i just really need some advice with my situation. i kinda feel like my girlfriend wheres the pants in the relationship and she does things that she says i cant do. i really do love her but she is liking turning me into a person im not. for example, she got mad the other day because she says im stingy. i asked her how and she says because i act like whats mines is mines and noone elses and nobody else can use what i have. then she compared me to her ex saying that he said he'll take her little sisters to the mall and chucky chheses and others and she wouldnt even have to ask. he would ask her if he could. i took them once but she asked to and i did. she basicallly saying she wish i was like her ex. which really pisses me off. she always brings up her ex's and compare me to them. but anyways, im not her little sisters parent. that their parents job but she gets mad because i dont take them out places and by them candy. the other day, her little sister was jumping all over my caar. i have camaro, and she was throwing sticks at it and i got mad and told my gf to tell her to stop and she didnt. she just laughed. i work hard for the things i have like my car and she doesnt respect my things. she also looks at other guys on the internet like famous guys that she thinks is hot and she like says they are hot right in front me. nut if i see a girl on tv and i do it, she gets mad. im starting to think that im just gonna use like her ex bfs and find another girl but i really want to be her. because i do love her. she even calls me the b word and i tell her to stop but she keeps doing it. i say it back so she sees how it feels and she gets mad. sometimes she wont even kiss me. she tells me she really loves me and just wants to be with me and only me and when we're together and everything is going great. i just never want it to end. but idk.. to i just need to put my foot down? lol help me