You can form a superlative by adding -ísimo(s) or ísima(s) to an adjective and even some adverbs. This can translate to mean very, really, extremely, super, or any other ultimate word you can think of. ¡Esa comida es buenísima! (This food is the best or very good!) Estoy encantadísimo. (I am extremely delighted.) Las chicas allí son bellísimas. (Those girls over there are really beautiful.) Los abogados estan ocupadísimos. (The lawyers are super busy.) ¡Llegaste tardísimo! (You arrived super late!) Caminas despacísimo. (You walk extremely slowly.)

When you add an adjetive -isimo, -isima you make a "superlativo" grade. That makes the adjetive bigger like you said with your example. Other examples: amable-amabilísimo rico-riquísimo mucho-muchísimo I can see that you know a lot of languages. Can you tell me how do you learn all the vocabulary and don´t forget it? Do you have any method or something like that?

you're right, it means muy guapa. It's the superlative form of the adjective. To form it, in most cases you just need to add the sufix "isimo" or "bilísimo". Guapo: guapísimo. Rico: riquísimo. Pequeño: pequeñísimo. In other cases, the whole word changes: Bonito: precioso.