Snoopy, Come Home

The film starts at the local beach, where Snoopy is partaking in surfing. He soon encounters Peppermint Patty, who decides to meet him at the beach the next day for lunch. Snoopy then returns home, much to the exasperation of Charlie Brown, who ends up cutting his thumb opening a can of dog food for Snoopy.The next day, Snoopy goes to the beach, but ends up being forcibly ejected due to a new sign stating that no dogs are allowed. Snoopy then proceeds home, where Woodstock composes a letter in regards to the new ordinance. Meanwhile, at the beach, Peppermint Patty is unsure why Snoopy hasn't showed up, but thinks she has been either 'stood up,' or that he doesn't have any interest in her.Snoopy later goes to the library with Charlie Brown and Sally, but is soon kicked out due to another 'no dogs allowed' sign. Snoopy, in anger, then goes out and attempts to take Linus' blanket from him, and gets into a boxing match with Lucy, with both of these endeavors ending against him.The next day, Snoopy receives a letter in the mail, and much to Charlie Brown's surprise, Snoopy summons Woodstock, and the two immediately leave. Charlie then shows the letter to his friends, explaining that it is from a girl named Lila, who has been in the hospital for three weeks, and requests Snoopy's presence. However, none of the group have any idea who Lila is.Linus decides to do some investigating, and calls the Daisy Hill Puppy Farm. What he soon finds out is a shock to Charlie Brown, as Charlie is not Snoopy's original owner. Snoopy was bought by Charlie Brown's family in the month of October, but Snoopy had previously been purchased by another family that August. The family had a daughter named Lila, but due to the family having to move shortly after Snoopy's purchase, they returned him.Meanwhile, Snoopy and Woodstock continue on their way, passing through cities, neighborhoods, and through the countryside. Along the way, they encounter all sorts of places that have signs saying 'no dogs allowed,' and even a little girl who attempts to claim the two as her new pets.Finally, the two friends make it to the hospital where Lila is, but are confronted with a sign out front that declares "no dogs or birds allowed." The two end up sneaking into the hospital, and Lila is happy to see the two of them.However, Snoopy's visit soon turns heartbreaking, when Lila expresses hope that he may be able to live with her and her family again. On the last day of his visit, Snoopy is about to leave, and then decides that he will accept Lila's proposal. Lila eagerly tells Snoopy that he can go back to his home and say goodbye to his old friends, before joining her.Snoopy and Woodstock journey home, where Charlie Brown is thrilled to see them. However, Snoopy's first act being home is to write up a paper, bequeathing certain items of his to some of the kids. Schroeder is to get Snoopy's record collection, and Linus is to get Snoopy's croquet set and chess set.The day before he leaves, the kids throw Snoopy a farewell party, in which everyone is sad to see him go. The next day, Charlie and Snoopy have a tearful goodbye, with Charlie spending the rest of the day in a depressive funk, being unable to eat or sleep.Meanwhile, Snoopy has gotten to the apartment where Lila lives, but finds two things that cause him to reconsider:1) Lila also owns a cat
2) The apartment she lives in has a 'no dogs allowed' signSnoopy happily heads home, where the rest of the kids and Woodstock eagerly welcome him back. However, their welcome soon turns to scorn when Snoopy writes a new note, requesting all the items he bequeathed to the kids be returned."That does it, Charlie Brown," exclaims Lucy, "He's your dog, and you're welcome to him!"

Question: Who did Snoopy get a letter from?
Answer: Lila