I rarely start a thread but am worried about DD1 and am hoping for some reassurance from the wise MN collective.
DD1 is nearly 4 has always been a sensitive soul, not so much shy, but more quiet and thoughtful, the sort that rather be in the middle of things, is quietly watching with enjoyment or doing her own thing. (puzzle, book and the suchlike) Pre school and friends often comment on how sensitive she is and I have often found myself hoping she would assert herself more where other children are concerned as it breaks my heart that she is often the one that is picked on. I tell myself all normal for her age and children are children and it usually balances out over the next few years.
She has never bitten/hit lost her temper with us or other children and is far more likely to cry and get upset if she gets frustrated (this happens frequently and easily, more so lately)
Sorry for the long background but it leads up to my concerns.
DD2 was born 6 weeks go, DD1 was/has been very excited and seems to adore DD2. However I have noticed DD1's behaviour change over the last 2/3 weeks. I know the enormity of a sibling arriving affects most children's behaviour but DD1 seems to have manifested as anxiety and dark thoughts 
She has always been sensitive to taste (fussy eater) and sound (extreme fear of hand dryers will cover her ears and cry in public toilets) these have gone through the roof the last few weeks, food especially and she has started saying all food is getting stuck in her throat and making her cough so she is eating very little. She also keeps asking me to check her mouth for bees/hair/other objects.
The thing that really concerns me is that she keeps making comments such as 'you can't poke a baby in the eyes can you mummy? you can't poke their eyes out' 'you can't pull their hands off can you mummy? that would not be nice would it' It's never said in a sinister way, very matter of fact but sometimes very dark all the same.
It's horrible to hear her say things like this and really hard to see her obvious anxiety and obsessiveness over the smallest thing

DD2 is a very laid back baby so DD1 is not missing out on attention/one one time.
I'm really worried about her 
If you have got to the end of this epic post, thank you, any advice you can give will be truly appreciated.