Learn Spanish (Latin America): ¿La puedes planchar pronto?

When you have a conjugated verb (puedes) followed by an infinitive (an unconjugated verb like planchar), you have two choices for where to put the object pronoun. You can put it right before the conjugated verb (la puedes planchar), or you can attach it to the very end of the infinitive (puedes plancharla).

So is ¿Puedes plancharla pronto? also correct?

Yes, absolutely! Both ¿La puedes planchar pronto? and ¿Puedes plancharla pronto? are completely correct, mean exactly the same thing, and are very common in everyday Spanish. You can use whichever pattern you find easier to remember.

How do we know la means 'it' here and not 'her'?

Context! While la can mean 'her', it is also the word for 'it' when referring to a feminine noun. Since you do not usually iron a person, la must refer to a feminine piece of clothing, like a shirt (la camisa) or clothing in general (la ropa). If the speaker were talking about a masculine item like a dress (el vestido), the sentence would use lo instead: ¿Lo puedes planchar pronto?

Would the word pronto ever change to pronta because we are talking about a feminine object?