Who is at the mall?

Question

My younger sister wanted to play a game with me.

She: You have to say a random word, and I'll tell you a number related to it. In the end, I'll ask you a question, whose answer will open a secret vault. You ready?

Me: Well yeah of course! Should I start?

She: Yup. Say a word.

Me: FOX

She: 15

Me: WITCH

She: 15

Me: HASH

She: 19

Me: MAT

She 9

Me: MINIMIZE

Waiting a bit

She: 21

Me: LOCK

She: 20

Me: CLOVE

She: 23

Me: DONE

She: 23. Oh I mean are you ready for the question?

Me: Yup

She: WHO IS AT THE MALL

Me: How will I know?

She: It was you who took the challenge. Tell the answer, or......

Me thinking........Puzzling.SE!

P.S. This is in no way related to any of the questions I've posted recently here

Edit (after accepting the answer) The great minds discovered that the secret vault had spaghetti. Even my sister couldn't figure it out. Of course as usual she forgot to plug in the microwave. :/

Answer 1

First notice that:

Me: MAT She 9 Me: MINIMIZE She: 21

This is

The number of strokes required to draw the words in capital letters (M=4, A=3, T=2, I=1, Z=3, E=4)

Now

Me: FOX She: 15 Me: WITCH She: 15 Me: HASH She: 19

is interpreted

by O=10, C=5, S=10, which results apparently from a choice (a curve is not made of linear strokes, so it has greater value)

Note that this is confirmed by:

Me: LOCK She: 20 (2+10+5+3) Me: CLOVE She: 23 (5+2+10+2+4)

Finally

Me: DONE She: 23. Means that D=6

So the answer is

She: WHO IS AT THE MALL $$(4+3+10)-(1+10)-(3+2)-(2+3+4)-(4+3+2+2)$$ So if the answer is a number (as indicated in the comments below) it has to be $$17115911$$