Given what you've described, you may have to take a different approach --- at least, when your father is around. It's hard to tell what she's responding to or why, but, at this age, you don't want her developing bad responses to questionable behavior. And, I consider staring at a dog/puppy questionable behavior no matter how well-intended it might be. I find the fact that he'd corner an unknown dog to be concerning; that he doesn't understand how he caused the dog's reaction, I find alarming. I suspect that simply "asking" him not to do something isn't going to be effective.
I'd recommend crating the puppy (with toys and/or a yummy treat) in a separate room with the door closed and locked, if need be. If asked, I'd say something like "Puppy doesn't do well with strangers, so let her rest." And, insist that he leave her alone.
From my perspective, your primary responsibility is to protect your puppy so that she doesn't think that she's got to protect herself from people (e.g., your father) who don't know how to interact with dogs or how to read the dog's behavior. So, there are two things you want to avoid: Having your father get bitten and having your puppy learn that biting is an acceptable default in scary/questionable interactions.
I certainly sympathize with your predicament; clueless relatives and friends can be a trial.