The best way is for her to learn naturally, rather than in a forced or formal way (or with worksheets!).
If she doesn't already have alphabet puzzles or refrigerator magnets, please get her some (or ask Grandma to get her some for Christmas). When she plays with these toys, you can name the letters as she picks up or plays with them.
Get her some great ABC books (from the library is fine) and read those with her daily. My older son learned the alphabet from his ABC books when he was 2. Make sure that some of the ABC books have more than one picture per page. If the B page has baby, bottle, bug, bird, ball, book, etc. on it, she will hear that /b/ sound over and over as you read each word aloud.
Teach her how to write her name, and to name each letter as she writes it. If her name is Mary, then the letters M, A, R, and Y have special meaning to her. If she is interested, you can then teach her how to write the names of other people she loves.
I am a preschool teacher, and these are some of the things I have done with my children and my students.