Difference in meaning of the sentences

Mary talks as though she knows everything.

Mary talks as though she knew everything.

What is the difference in meaning between the sentences?


Mary talks as though…”

This implies that Mary does this regularly. I’m not sure of the correct term, but this might be what’s called the habitual aspect. It means she has done this in the past, and is expected to continue doing it.

…like she knows everything.
… like she knew everything.

The first sentence is MUCH more common. Both words, talks and knows, are continuous. Mary believes she knows everything, and continues to believe she knows everything.

The second sentence is a little awkward and weird, but not incorrect. Mary believes she knew everything about a specific topic, at a specific point in time in the past.

"She thinks she knows everything" is hyperbolic. It’s idiomatic and not literal.

She thinks she knew everything” can have more of a literal meaning. But it still has a hyperbolic idiomatic feel to it. That contrast makes the sentence weird.