Should i try to work things out or just leave her?

so i have been with this girl for only 2 weeks but we have 2 years of friendship together. we always liked eachother but not tell now done anything about it. so last night we had plans to go to dinner but they got cancled because of work problems. after she was done with work she stoped texing me for the night. this morning she texted me and told me after work she went to her ex boyfriends house for the night. he lives an hour and a half away. she told me she still has feelings for him and she goes up there weekly to hang with him. i like her alot but cant stand the thought of her driving that far to see some other guy. she said she likes me and they are just friends but i dont know. i want her but i am afraid that later on i will find out she was cheating on me with him or she will just leave me for him. WHAT SHOULD I DO?