¿quién era la más alta? lily eres la más alta. lily era la más alta. lily eran la más alta. lily eramos la más alta.

We often use adjectives to compare things, people, events, ideas, among others. This is used to compare nouns in three ways, comparisons of equality, comparisons of inequality, and in superlatives. This sentence stands for superlative. The superlative is a form of an adjective that expresses the highest possible amount of something talking about what is the most or the least. To form the superlative, we use the definite articles el, la, los or las and más or menos preceding the adjective. So the formula using más is as follows:

Most formula: definite article (el, la, los, las) + más + adjective

Here the definite article used is la and the adjective is alta.