I agree with Cindie here... and in fact, Beo, you "make" her happy by allowing her the freedom to be herself.
Lots of things probably "make" her happy that have little or nothing to do with you. Are you jealous of them? For example, here are things that "make" me happy that have nothing to do with a partner.
A sunny day outdoors
My job taking care of infant twins
My favorite TV show
When the Red Sox won the Championship
How my apartment looks after I do a good cleanup
Dancing with friends
IMing with my sister
You get the picture, I hope. Just because another person (or activity) is making her happy doesn't make you lesser. Life's a banquet. There are lots of things that make life worth living. One person and one person only can not "make" another person happy 24/7. If she were to die tomorrow, would you never be happy again? My dad depended on my mom to "make" him happy and he's been depressed for 3 years since she died. Is that healthy? IMO, no.
NRE can make a person feel like their love object is the be-all and end-all of happiness, excitement and perfection. This is idealization. It fades once you spend enough time with someone and start to see their all-too-human faults and unpleasant quirks.
Love withers under constraint; its very essence is liberty. It is compatible neither with envy, jealousy or fear. It is there most pure, perfect and unlimited when its votaries live in confidence, equality and unreserve. -- Shelley
Mags, F, 60, poly-dating, loving and living with
miss pixi, F, 38
Punk, 41, M (dating since Oct 2015)
and a few more casual relationships