(Sorry for the extremely long comment :P)

Okay...I'm gonna be honest with you. This is not a bad story by any means, but it does have a lot of flaws. Let's start with the good stuff: Selena was quite an interesting character, and it was cool to read about her dangerous/obsessive tendencies in the beginning. The fact that you didn't exactly tell us why she is killing all these people makes it more intriguing and makes her character deeper and ultimately more interesting, even though I thought you still could've gone into a little bit more detail (especially about the people she killed, because even though their lives might be worthless to her, they are worth everything to other people). At the end, I did like the message of embracing family over self, and I thought that it made the story more resonant.  Now for the bad stuff: this story does have a lot of grammar issues. Mainly it's punctuation errors and confusing certain words with other words ("their" instead of "there"; "your" instead of "you're"; "defiantly" instead of "definitely" which is actually a very common mistake for most writers), but there are also quite a few run-ons and you do have these awkward shifts between past and present tense. Easily fixable, but distracting nonetheless. Also, the characters other than Selena just didn't feel as important or real as her for varying reasons: Katie was very suddenly and awkwardly introduced, Dr. Welsh wasn't really described at all, and you could have gone into more depth about Sawyer's anger and selfishness. In general, you did kind of have a tendency to bring things into the story rather suddenly, like the woman in the plane that Selena had been telling the story to; that part really caught me off guard, and not in a good way.  This story has a lot of things going for it, and I did like those parts where its strengths were showcased (mainly in the beginning), but there were also a lot of things that need fixing. You are a good writer, and I have no doubt that you are very capable of fixing the aforementioned mistakes. Take this feedback to heart, and definitely keep on writing! :)

Awesome!! Interesting and exciting.

Kept me interested to the end. Liked the descriptive words used throughout. Nicely written. Very good story idea.