My daughter and my nephew both had problems with L sounds when they were little.... actually my daughter would still pronounce it as a "w" sound until she was 6 years old!
Here is what I did to help. I made a puppet and gave her a funny "L" name (our puppet was named "Loopity") She spoke with an exaggerated British accent and had big loops of yarn for her hair. (She was just a crudely made sock puppet!)
"Loooooooopity" would only say funny things if you tried to pronounce her name correctly. She would come out particularly at bathtime (as an added bonus) to tell you NOT to wash your toes because she LOVED to smell the toe-jam, and she LOVED wax in your ears too.... etc, etc.
It encouraged the kids to practice their L's, they saw my mouth doing big exaggerated L's, it was fun, and the reverse psychology encouraged them to wash too! :)
I would only seek help if she CANNOT pronounce an L the correct way. If she struggles and struggles and just physically CANNOT say an L, then seek some speech therapy for her, but most likely she will outgrow it. This is a common letter for that age to mispronounce.
(Both of the children I mentioned had problems with R's too, and they were also resolved at about 6 yrs old with lots of practice and reminding.)
Hope this helps!
Amanda