How old is Hellen?

Everyday that my house helper Hellen comes I ask her if she has found out her birthday yet. I make some smart aleck comment along the lines of, "Hellen! today could be your birthday, what if it's today and I haven't even gotten anything for you?" Then she proceeds to try to call her sister who stays with her mother to find out when her birthday is. Usually the cell network is down so she's not able to reach, then if she gets through to someone either they are out of the house or the mother is. Hellen knows she was born in 1979. But that is all. She doesn't know the month or day, but thinks her mother does. Earlier this week her uncle called me looking for Hellen, after telling him she had already gone back to her home, I asked him if he had found out when her birthday was. He said it was February 2. I began rejoicing that we finally solved the mystery, but then he added, 1975. I remember that Hellen knew clearly that she was born in 1979, so I asked him if he was very sure, he said yes, that that was the correct date. I hung up not super convinced now that the mystery had been solved. I called Hellen and asked her, she stood firm on the year of her birth being 1979, as she said, her older sister, the one that had died already was born in '75. hmmm...so now is the day right and just not the year? or is the year and day right and hellen just always knew wrong? It would be quite the shocker to think you're 32 only to find out you're really 36. So now, I think we have to communicate directly to the mother and see if we can't solve this mystery yet...until then, I'll just keep giving Hellen a present everyday I see her, just in case (I know she's missed out on at least 32 celebrations...and maybe even 36). If anyone wants to guess the correct date, i can give a prize to the closest person...here's a photo of her to help you in your guessing...