My sister just had a miscarriage. How do I show my support and love for her? I am so worried for her.

I'm so sorry to hear that.. I think just letting her know that you are available if she needed someone will be sufficient. She will probably need some time to come to terms with the situation. A simple "hi" over WhatsApp or a phone call in the evening for a short chat may help. Simple gestures to extend the invitation to chat if she needed it. However, if she had made know that she would prefer to be by herself, respect her space and only check in once in a while just to see how she is doing would be good. If you feel like you would like to do something, you could make a tonic soup or some porridge and bring it over to her.