I think it's normal to be MEGA excited about something at the beginning and then it tapers to a steadier, calmer kind of feeling.
Falling in love with someone creates a physiological response in our body, releasing a load of oxytocin (for nice romantic feelings) and also cortisol (the stress hormone). It's why the honeymoon period is a thing - we go through a physiological experience as we gain strong emotional attachment and it creates a more heightened feeling.
On a more interpersonal level, there's an element of newness and excitement to a new relationship that eventually wears off - not because it's not good, but because it's not 'new' or unsure any more. You replace AHH NEW PERSON with 'this is my person' - you're more secure, you're not wondering if it's going to work or go anywhere, it IS working. That in itself is romantic - the idea that you're settled in the relationship and support each other on a deeper level (like emotionally, with your achievements, etc) rather than just the shiny newness.
It's a good thing, I promise you: as long as she's being a good, supportive partner and your emotional needs are being met*, this is just totally, totally normal.
On emotional needs being met - she's supportive, consistent, cares about you and your plans, is still in regular contact, etc, and that expecting the same level of 'new relationship' feeling to stay forever is potentially unrealistic, but you are allowed to express if you're not feeling that your needs are being met: try and identify what it is you're actually asking for, if you want to have that convo. Is it that you need reassurance, you want emotional closeness through words, etc? Rather than "You never send me nice texts", try "I'm feeling less secure in our relationship because things have settled down out of the honeymoon period and I want to make sure we have quality time/it's important to me that we express our feelings in words".
DH has a whole roster of silly nicknames for me, none of which are remotely romantic-sounding, but I'm also very secure in how he feels about me because he shows me every day in other ways - a warm towel out of the dryer just as I'm getting out of the bath, his commitment to making our home nice and helping me/doing decorating even though he couldn't care less about interiors etc. So look for how your partner does make you feel loved: if you still feel there's something missing, talk to her, but it's good to remind yourself that love isn't soppy texts. Love is showing up for someone and being there consistently and understanding what's important to them.
(Last point in this very long message: have you had less-good relationships before? Some of the things you mention - being happy when you see friends, not jealous, not saying nasty things - are really baseline stuff and while it's good she's that way, that should be a given. Often people end up in relationships where what someone says - nice words, soppy texts - say one thing (so you think it's love, and all good) and then do another - jealousy, nastiness, sulking about friendships. It can confuse things in your head and you confuse the lack of OTT loviness as it not being 'real'. Maybe I'm off base, but don't forget these things should come as standard in any good relationship, and the soppy stuff is extra - not a replacement for the real elements of a relationship)