Solving Riley's sister's name by math?

Ok, now that we finally made it to vacation time, I found myself awake at 2:30am. For too much of the summer, I was typically trying to solve an interesting problem at that time, so it seemed the process hadn't worn off quite yet. I was just itching for something to puzzle over. :)

We still haven't figured out a name for Riley's sister. So, I said to myself, alright, what kind of formula could I apply to generate Riley's sister's name?

So I started with J as the first letter of my first name and R as the first letter of Riley's name.
The difference is a positive movement of 8 letters, so I scored it as +8. (J=10, R=18).
I then took the minimum distance in months from my birth month to his as November->March. One can describe this as a positive movement of 4 months, so I scored it as +4.

This yields a +2 letter movement per month movement (+8/+4).

Riley's sister is due to October, which is a negative shift of 1, to equal a scoring of -1.
Which means that Riley's sister's name should be -2 letters off mine, or begin with an H.

To calculate the middle name, Riley's middle name is Scott. This translation can be described as the sign or magnitude of the first name's calculation, or +1 (R->S == +1).

Following this then, Riley's sister's name should have a middle name that starts with a G.

So how about Hailey Grace Dixon?