I can no longer remember her face, too much time has passed.
I can no longer remember her face; too much time has passed.
No. The first is a comma splice. Both I can no longer remember her face and too much time has passed are independent clauses. They should be separated by a colon, semicolon or period, or linked by a conjunction. An excellent choice for this example is for:
The second example is grammatically correct, as both independent clauses are aptly separated by a semicolon:
Here is the Strunk & White (Elements of Style) reference: