Opinion on dating your best friends enemy?

So long story short, my best friend who is female has a cousin also female. They do not really like each other and my friend did not approve of me talking to her a year ago. Well we ended up talking a month back. We have just went on our second date and we are hitting it off. I really like this girl which is really rare since my break up a couple years back. She’s the first girl I have found even remotely interesting and I just want to keep seeing her but I feel bad about my friend. They are are close family but their relationship isn’t great.
Opinion on dating your best friends enemy?
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