I'm going to guess she looks like either you or your husband somewhat ... she has your genes obviously.
My MIL used to say one of our kids look like her other son. The worst part is, my son hates being told he looks like his uncle - who is middle aged and never dated. No teenager wants to be compared.
We just ignore it. We told our son to do the same. She hasn't taken the hint, but then, people like that who are a tad odd, or socially awkward, rarely do.
Don't let it get to you. It's nothing personal.
I think you're overthinking this. I get told all the time I look just like one side of my family. It's because I am very small. That whole side is very little. My physical features are nothing like them. We just have the same physique. She's not an expert on this. She's just thinking of something to say when you're in her taxi. Some people talk to fill the void.
Change the topic is all. Don't let it get to you.