Did TT 7 cover pre-Algebra? Is she ready for abstract math at age 13?
One thing you could do is have her take the Algebra readiness test from the IOWA. It is short and Bob Jones sells it. You can score it and have the results instantly. I thought it was a good test for showing mental preparedness needed for Algebra.
She may, or may not, be ready for the type of thinking needed for Algebra.
I find Algebra goes well if they are solidly ready for abstract thinking, and if they are quick at basic math, percents, ratios, integers, etc.
My oldest liked Saxon for Algebra. My others like BJU. I have found them both to be great for mathematics.