I think my boyfriend likes my sister or am I overthinking?

So my sister is only a few years older than and I'm the youngest. Me and her don't have a great relationship. We always fought etc. I knew my boyfriend for years and We recently started dating. He works in a store and one day when we were going to the store, I was in the passenger side fixing myself in the mirror and she said "he will think im prettier anyway". That comment stung because I always thought I was the ugly sister. She shops at that store frequently so it has me thinking what made her feel that way. What made it worse, was when my boyfriend said "I saw your sister today, the one that looks just like you" I tired not to feel any type of way but it has me feeling insecure. Tell me if I'm overthinking it.

I think my boyfriend likes my sister or am I overthinking?
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