New Delhi, Dec 9: Prime Minister Narendra Modi on Sunday extended his greetings to former Congress President and UPA Chairperson Sonia Gandhi."Best wishes to Smt. Sonia Gandhiji on her birthday. I pray for her long and healthy life," he tweeted.Gandhi was born on this day in 1946 and has been the longest-serving president of her party for a record 19 years from 1998 until her son Rahul Gandhi took over in 2017.While studying in England, she met former Prime Minister Rajiv Gandhi. They married in 1968. She took over as the party chief seven years after her husband's assassination.