The "I love you" Syndrome

My family has never been an emotionally expressive one. It has never been a cold family, don't get me wrong, we have always been laughing, we always used humour to express our affection for each other and i always thought that was grand. I never doubted our love for each other, it was even more valuable for not being mentioned, it was so wonderfully beyond need for expression, it was perfect.
About a decade ago my sister lost all notions of a sense of humour and slumped into a depression that she is not yet out of, though at least now she tries, and my mother has never ever been a mushy woman, i honestly don't recall hearing the words "i love you" from either of them up till two years ago, ma out of being her, and my sister out of being angry at the world.
All that changed when i moved to France, my mother turned to goo, all of a sudden "I love you" became the natural ending of every sms, and every sentence when i was home. I got an email yesterday from my sister with her passport details, signing off with "i love you", and a scan of the passport today, also ending with "I love you".
WTF?!
I am not a cold person, i assure you i am not, and if you browse through this blog on any two random posts you will find me emotional and way too intense, i am always hugging my friends and telling them all the time how much i love them and they do the same, HOWEVER, i don't think that it's fair to change the family's way of relaying love after 24 years.
How am i supposed to react to this? I don't know why, but i can't really deal with it, i find myself replying to the I love you's mechanically, and hardly ever initiating them. I love my family dearly, but this just isn't the way i'm used to expressing it, i'm sorry if i'm a bitch, but this avalanche of over used "i love you's" just annoys me.