Use of the gerund

Question

I want to say "I met Rosa leaving the theatre", in the sense that Rosa was leaving the theatre. I've written "Me encontré con Rosa saliendo el teatro" but I think that means that I was leaving the theatre when I met Rosa. However, "Me encontré con Rosa al salir el teatro" feels completely wrong, and "Me encontré con Rosa que salía el teatro" sounds right but a bit formal. Is that last translation the only way of removing the ambiguity.

Accepted Answer

Hola Gordon
Your first sentence "Me encontré con Rosa saliendo del teatro" can mean both, you were the one leaving the theatre at that moment or Rosa was leaving the theatre, so, to specify in order to make it clear you can just add the pronoun with a "cuando" clause. In this case, the pronoun has a clarifying function, so it won't sound redundant: "Me encontré con Rosa cuando ella salía del teatro".
Your other sentence "Me encontré con Rosa que salía del teatro" is correct if you add a comma, so it clarifies that it is her leaving the theatre: "Me encontré con Rosa, que [= la cual] salía del teatro".
The option with "al salir" is correct too. It would be ambiguous though, unless you add the pronoun right after:
"Me encontré con Rosa al salir yo del teatro" 
"Me encontré con Rosa al salir ella del teatro"
I hope it helps 
Saludos
Inma

Answer

Thank you, Imma. That makes it very clear and I've learnt a few more useful constructions.