You’ve done a great job characterizing a young Tom. You’ve added some great details which are just logical based on what little we know about him as a first year. (ie I’m sure he watched every aspect of wizards in order to emulate them.)
Ximena is an interesting character, a bit of a kindred spirit, if Tom every had such a thing. I like the way you kept us in suspense as Tom attempts to decipher her actions and motivations. It would be interesting to see her perspective. Does she consider him a harmless kid that can hang around, a friend or someone to use?