What does it mean when she says she doesn't want to ruin our friendship?

I just asked out my best friend of 7 years. She knew I had feelings for her for awhile now and she just admitted she has feelings for me, we kissed so I asked her to be my girlfriend but she needed time to think. After about 3 weeks she told me she wanted to date but didn't want to ruin our friendship since last relationships have ended badly. Should I just stay her friend and give up or is there some hope?
What does it mean when she says she doesn't want to ruin our friendship?
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