[name]Do[/name] you think that [name]Milly[/name] could be a nn for [name]Matilda[/name]?
Bit of a stretch but I can see it. I’d be more likely [name]Mattie[/name], [name]Tilly[/name] or [name]Tilda[/name] though. I love [name]Milly[/name] as a nn for [name]Millicent[/name]!
Whenever I’ve heard nn [name]Milly[/name] in use it has been almost completely unrelated to the fn. I’ve even heard it used as nn for [name]Amanada[/name]. [name]Milly[/name] for [name]Matilda[/name] seems like a natural choice.
[name]Maddy[/name] would also work.
[name]Tilly[/name] and especially [name]Tilda[/name] seem a bit dated to me.
If [name]Tilly[/name] can work, why not [name]Milly[/name]? I think that [name]Milly[/name] is a darling nickname for [name]Matilda[/name]. 
Good luck!
Yes. I think it would work!
Yes, I think it works.
Absolutely!