So I know Nyx is considered a jealous Goddess. So, would it be wrong to worship other Goddesses as well if I'm already worshipping her?
With only my experience to add to this question, I’ve found that, although jealous, Nyx is still loving. She is a mother with a temper if you will. I really only pray to her, but I’m sure it would be fine working with other goddesses, so long as you don’t just lump her in with them. Maybe do something special for her afterwards if you really feel worried about it. She might be a little petty and not talk to you for a little bit (I’ve learned that the hard way, hence I usually only pray to and worship her) but after some apologies and even the smallest offering of some sort (I aim for dark chocolate and usually only try and find poppies if I really messed up.)
But she’s still a kick-ass goddess to work with, and she’s shown me considerable kindness over the past 6 years.