Do they sound natural?
1) Her behavior and movements were consistent with my belief that she had a boyfriend.

2) Her behavior and movements were obvious enough to me believing that she had a boyfriend.

Question

Do they sound natural?
1) Her behavior and movements were consistent with my belief that she had a boyfriend.

2) Her behavior and movements were obvious enough to me believing that she had a boyfriend.

Answer

The first one is fine, but the second one no.

Maybe: Her behavior and movements confirmed for me that she had a boyfriend.
Or: Her behavior and movements made it apparent to me that she had a boyfriend.

I hope this is helpful.