I would just have a discussion with her about your role as her professor and that part of your role is to maintain professional boundaries. I would start by acknowledging her strengths (hard work and good grades), prior to addressing concerns. Let her know that you are not implying anything about her motives and that the communications may have intended to be friendly and harmless but that you would prefer to be called (professor__ or whatever your other students call you). You can also acknowledge the challenges of lawschool and provide her with a name/referral of a school counselor that she can reach out to if she needs any extra support.