I own Utena Tenjou, a fanpet named after the title character from Revolutionary Girl Utena (wiki link!)

(I can provide more images/info on the character and series as needed!)

I've never seen the series (although I know who Utena and Anthy are), so the personalities of these suggestions might not fit... mostly I'm going by color.

Dawn Demi

Dawn Donadak (probably not serious enough, although the picture you posted of Utena looks a bit more playful than I thought she was!)

Dawn Feli

Sweetheart Demi (again, probably too playful)

Angelic Lain

Most of the Sweetheart pets, and some of the Dawn, are perfect for hair and eye color, but the Sweethearts are mostly too cutesy I'd think :P But I hope this helps, or at least gives you some ideas!

Here are my suggestions:

Nostalgic Irion is my number one pick, because of the expression, feminine look and pink flowy mane.

Also, the obvious sweetheart pets!

Sweetheart Antlephore has the pose spot on!

Sweetheart Escalade because they look humanoid in colouring and have that mischievous expression

But if you're looking for something other than sweetheart, I'd say...

Spectrum Lain, because of the pink wing tips and feminine expression!

Hope I could help!

Oh, I actually really liked the Dawn Demi and hadn't considered it before as I already have one. Hm, def gonna me mulling over that one and seeing if I can customize it a bit with an overlay or something, idk. The angelic Lain also looks really nice for her, I don't often look at Lains so I hadn't considered one. And yeah, Utena is rather serious a lot of the time but she has her moments of being sort of silly. She has a strong sense of right and wrong, and despite enjoying playing the role of the prince/hero type she does have her "normal teen"-esq moments.

Thank you for all the suggestions. I'm not against sweetheart pets but I already have quite a few so I am sort of leaning away from them, though I do like that Sweetheart Escalade! The Lain you suggested is good too, I'm going to have to go take a look at all the Lains and give them more consideration.

Thank you both so much for all the suggestions. I'm still not quite sure (and I have to leave for work soon) but I'll definitely be thinking over all these and using this thread for reference while I consider my options. :D

i actually think the reborn Demi kind of suits her. it's effeminate but in a powerful way, just like Utena. the series is about strength and changing/revolutionizing the world so i think a reborn pet matches thematically. maybe an overlay where the demi's color-scheme was more fitting to Utena's might draw you in?

Yeah, tbh all I've really been looking at are other reborn pets, like the Jollin and Malticorn, but none quite click completely for me. When I have some time I'll try to see if giving the Reborn Demi the colours of a dawn pet/similar colours will make it feel more fitting. Because yeah, thematically I really like the idea of a reborn pet but I've been looking at them so much that I feel almost stuck in a rut haha. Thanks for the feedback and suggestion! I'm glad I'm not the only one who thinks reborn would be a good colour for her. (It's part of why I changed the name of the reborn Demi I already owned instead of making a new pet. I liked the idea of her being a reborn pet, but I haven't quite been able to stop seeing her as "my old pet I renamed Utena" instead of "my Utena fanpet", if that makes sense.)

Malticorns actually reminds me more of Anthy, because of her hairstyle, haha. a reborn pet would also look good if you photoshopped some rose petals swirling with the flames. but also, what about a glade pet? they definitely match the anime's rose imagery. i see Anthy is already a glade Jollin, so you might not want to have another glade pet, but at the same time maybe it wouldn't be so bad to have them match considering how close they are. since Utena's original goal was to be a prince, a Legeica would be a nice fit since princes ride horses and they already have the nice long hair you'd just have to photoshop pink. a reborn Legeica would also work if you think their expressions fit Utena. (i personally don't really like them personally but it's nothing a simple overlay can't fix)

That's fair, it's really mostly the pose/attitude of the reborn Malticorn that I've liked-- it's sort of protective in it's stance. Not enough to go "that's it!" though (hence the thread haha~) Another glade would be fine (it's multiples of the same pet I'm not as into, species and colour multiples still feel different enough to me) I actually hadn't thought of glade for Utena. I'm kind of digging that glade Legecia. It'd need some photoshop/an overlay but the general idea is interesting. Sort of calm/passive for her but matching glade Anthy and Utena pets would be pretty cute. (Not a huge fan of the species so I hadn't really looked at any.) Thank you for the ideas! I'm gonna have so much playing around to do when I can get a day off from work~

To be honest, Dawn demi was what I was going to say too since it fits the show theme. I remember a lot of pink in that anime when I watched it.

Also, angelic jollin or Irion because they both look kind of princely and regal.