Honda Civic LX 1998. Should I keep or try to sell?

So I have a Honda Civic LX. She is 20 years old with about 70,200 miles on her. I bought the car from my grandma about two years ago with about 50,000 miles on her. My sister and I both learned how to drive on her. My grandma drove the car very little in its first 18 years. Since buying her, I Drive it daily to and from work, sometimes twice a day. I usually drive between 8-20miles a day, give or take some.

Since buying her two years ago these are the repairs I have gotten done
- new muffler
- some new belts (not quite sure what they were called
- new radiator and water pump
- new timing belt
(And possibly another thing or two, just can't think of it all)

She is now making a rattle sound in certain rpms and a buzzing sound when accelerating. I'm going to take her a mechanic this week, but i'm guessing she needs a new exhaust system/catalytic converters.

In your thoughts and opinions, should I spend the money to get her fixed? Or just drive her until she can't be driven and look for a new car? I've sunk atleast three thousand into and not sure it's worth it to sink anymore. Do you think she has more life left in her- a year, two, three? Think the motor is good since it is low mileage.

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