Introducing 2 male chihuahua's?

[?Rose?]

He ya.
I have a 6 month old Chihuahua MALE named Ollie.. he knows i am his alpha female.
My mum fell in love with my Chihuahua and brought one of her own.. who is also male. ( max ) he is 4 months old.
My dog goes absolutely nuts for Max, wants to play and carry on.. but max is not interested at all and just growls at him all the time! Could this be because of the way he is approaching him? he sort of charges and looks over him, i know this is dominance.
How can this behaviour change? we were really hoping they would get along and play together as good mates. How should i be punishing my dog when he shows dominance over my mums dog, and should my mum be growling at her dog when he bites and growls at my dog??
This is a nightmare.. constantly telling my dog off.
Should i just let them go for it ?? Worried things could get a bit messy lol. How can i deal with this? and what is acceptable from my dog?