As children learn to talk, there are certain sounds that may be more difficult for them to pronounce at younger ages. Many children who are 3 and 4 have difficulty correctly pronouncing the /l/, /r/, and /th/ sounds. For most children, by the age of 5 or 6, and sometimes even as late as 7 years, they self-correct these sounds and learn to pronounce them correctly.
At 4 years of age, your daughter may still not be developmentally ready to pronounce these sounds. At this point, if those are the only sounds she is having difficulty with, you may wish to hold off on having her evaluated. However, if she is continuing to have difficulty by the age of 5 or 6, an evaluation by a speech therapist would be warranted to see if your daughter needs extra help learning these sounds.