Need opinions pls + could gf's father alcoholism affect the future?

Need honest opinions pls. So my gf is my sister's friend too and i've known her through my sis and I love her but I don't feel like getting even engaged to her at all and it makes me feel guilty. So i've known from the start that her dad is alcoholic (she's not the one who told me, my sis did) and at first I didn't care as I wasn't being that serious about our RS but now i am. Is it a red flag that my gf hid this from me? I asked her and she said she didn't wanna talk about it. I have many fears, like what will people say about me if we get married and it'll ruin my reputation and many relatives said to leave her as it might ruin our family's reputation too as we don't have history with alcohol at all(we're not that conservative tho). Im also afraid she might take after her dad also i've read that alcoholism can get passed down as genes. I feel bad for judging her because of him but I'm confused and idk should I break up or what to do? Another thing is i'm getting older and this is prob the only serious RS i've been in. Any advices please w y3aychkom.