The comments about Erika are true, she's the best host ever!
She knows better than anyone how to welcome you and make you feel comfortable. If you need anything, she'll always be there to help (she knows Barcelona perfectly).
Even if her English is not the best, there's absolutely no problem, by switching language (we did French-Spanish-italien-English mixture) we understood each other and every recommandation or was really easily.
A big thank you to her, we've spent great days at her place !