This card, Goldberry, River-Daughter, could be beneficial in a deck focused on ramping up mana quickly or in a deck that utilizes a lot of blue spells
While card types like enchantments or artifacts do help to minimize Umori, the Collector's drawback since there are artifact / enchantment creatures and removal spells, making it possible to make a semi-functional deck with Umori as its companion, even in these cases, a decent body that offers a slight discount on your spells doesn't seem worth the effort
This can occur during the same turn you gained your initial speed
This is the Perfect Commander deck if you enjoy generating value, drawing cards, and accelerating so that you can bash in with huge creatures.
Id also be curious to see what the combination would be for your moms deck, if you want to find us on Twitter to let me know
however, whether or not that happens remains to be seen