Lilina (LA)

Give her a speed refinement for green gift so she has 35 speed + 5 equals 40+3 and summoner support gives her 45 speed and water equals 48 and Calvary buff gives her 54 speed with attack she has 47+5=53+2 55 attack plus Calvary buff 61
attack with 18 defence and 20 res

With perfect IVs like +SPD -DEF, I was able to turn Lilina into a perfect glass canon by using Life and Death, which is great because truly offensive green tome horses have been missing in this game for a long time. You can use Ardent Sacrifice to heal and set herself up for Desperation, since even without Life and Death, she probably can't take a single hit.

Merge: +2
Seal: Speed +3 (40 Speed while equipped; 37 without)

Player Phase Valentine's Lilina

Pros:
+ Very serviceable Attack and Speed for a Cavalry Mage, much better than Cecilia's in comparison
+ Can make great use of Gronnblade+ build very effectively, especially in a full Horse Emblem team
+ Can 1HKO certain Red units after Hone & Fortify Cavalry buffs while Gronnblade+ is equipped

Cons:
- Has paper-thin defensive stats (low HP, Def and Res altogether)
- Needs to rely on Fury to safely lower her own HP
- Needs to rely on buff support to truly deal damage and make powerful follow-ups
- Truly works best in full Horse Emblem teams, but works decently outside of it requiring Dark Azura's service or those with Tactic skills to get anywhere
- Weak to horseslaying weapons (also weak to the rare Kitty Paddle+)

Side Notes:
+ Functions like Summer Elise on horseback; great Attack stat, but middling Speed stat and can effectively run a typical Bladetome build
+ Fun to use, plus she is very lovely in all of her artwork
+ Easily replaces Cecilia due to having better offensive stats and able to run skills that Cecilia could not
+ With an IV spread of +Spd/-HP, she is very flexible to build, plus she retains her overall BST weight
- Does face competition with Gunnthra as a Green Cavalier herself

(Most optimal build, stats are +atk -def, with weapon and seal)
Personal thoughts:
With a neutral 35 Atk, LA Lilina has a lot to offer than meets the eye at first; so don't feel bad if you got her instead of Hector.(But I do feel your pain.)
1. At neutral 35 Atk, Lilina ties with Sigurd and Brave Roy(with his Blazing Durandal) for the highest Atk stat for a cavalier unit, the highest Atk of all of the Ranged Cavaliers, and 3rd highest among all the mages.
2. While 30 Spd is not as flashy as you would like, it's actually not that bad for a high Atk cavalier. Since Cavalry units have lower bst than the other movement types, their stat spread most of the time can screw them over. High Atk cavaliers such as Reindhart and Xander suffer from extremely low Spd, which not only limits the possibilities for their player phase but also makes them more vulnerable to enemy attacks since they are more than guaranteed to get doubled by almost every unit; while Cavaliers who have a Spd state between 33-35, most of the time suffer from having a low Atk. So this means an offensive Stat Spread of 35-30 is actually not as bad as it sounds.
3. Having high Atk and access to Tomes, grants a lot of versatility, and can be customized to what your team needs:
Heavy Nuke: Gronnblade+( Can be built to be a One Shot nuke, more optimal for Cavalry teams, or the regular Blade tome set which focuses on doubles since her Spd is actually salvageable)
Anti-Colorless: Gronnraven+( While not as good at baiting for obvious reasons, her high atk allows her to One-Shot a lot of colorless and blues or do a number to them, making her a great candidate for Vantage since she does not have to rely on Quick Riposte most of the time to kill her target, her much higher speed compared to other common Raven tome units also doesn't hurt, and she can still run the Quick Riposte skill instead to secure the kill or the seal to combo with Green Tomebreaker.)
Anti-Cavalry: Keen Gronnwolf+( While Micaiah and recently Caeda have better weapons that also counter Armor units as well, there are some few things to consider. Comparing to Caeda, Lilina has lower Speed, but has way more Atk, and she has a magical weapon which targets the majority of the Meta games lower Res. Comparing to Micahiah, having the same Atk and Spd, are mostly on par, but Lilina has a better color that fits into the meta, with Blue and Green units being more common, and her better mobility allows her to reach her targets faster, or escape a physical threat much better; however both are extremely effective in taking on the Brave Ly+Reinhardt combo which is extremely common in arena, not to mention Micaiah is an incredible and effective mage tank which is something Lilina can't do effectively.)
Overall an incredible Green tome Cavalier who not only does not have a lot of competition for a team slot to begin with, is an incredibly versatile unit capable of fulfilling any role your team needs.

Let's be realistic: this is the only real set LA!Lilina can run consistently. Possessing the highest attack of all green tome cavaliers and decent speed that can be buffed, Lilina is a terrifying threat under horse emblem.

The set is a standard LaD Desperation to boost her speed as high as possible while also boosting her attack. Should the player have an attack boon Lilina instead, they can opt for a Death Blow set with G Tomebreaker to go for pure one shot attacks, as Lilina desperately needs every point of speed available to be able to reliably double opponents.