Thanks guys
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Actually, she'll hate it! She's only one year old and very possessive of her parent's attention. Once it shifts to the new baby she'll be very jealous, possibly leading to her fostering a subconscious hate for her younger sister until she is in her teens, where they'll both absolutely hate each other and cause all hell before resolving it...
On that note, good luck!
Two of my younger sisters are 11 months apart (15 and 16) and they are best friends, and have been they're entire life.
These are extracts from the Colorado University testing they did:
Research at Colorado State University, for example, has found that for firstborns, having a younger sibling born two or more years later dealt the older child a blow to its self-esteem, while having a sibling born less than two years later did not have that effect.
The Colorado group proposes that this may be so because a child raised alone is privy to all his parents nurture and affection. The longer a child has to get used to this relationship, the more negatively he will experience the birth of a younger sibling. However, if the child has reached the beginnings of independence at the age of 5 or 6, the birth of a younger sibling no longer seems to have the same psychological impact.
Basically, what they are saying is that based off the testing, it is more likely for that jealousy or hatred to occur when the siblings are around 2-4 years apart.
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That or neutered 
