You will ideally want to use either Amarna or Twilight
Twilight gives a nice resistance debuff for 5s on using her support skill
Amarna gives a nice ballistic buff for 15s and an ATK buff for 1.5s upon her support skill dealing damage
Fritia can maintain both of these buffs pretty easily, but which of these is more useful depends on what you are fighting and what other sources of resistance reduction and damage buffs you have.
In practice you might want to simply pick whichever of the two you find easier to acquire and use that - you'll likely transfer the logistics squad from Little Sunshine over to a 5* support operative who can use it when you gain such an operative.
Since both Amarna and Twilight are both viable for some 5* support operative at endgame, both are fine for this purpose.
As such, don't worry too much about which logistics squad Fritia uses - you'll probably end up swapping them out later anyway.
Similarly, it's not worth re-rolling Little Sunshines logistics stats - those re-rolls are better used on 5* operatives.
If you are using Little Sunshine as a support because you don't have any better 5* supports or much investment into your other operatives, then you are likely not going to have much resistance reduction, in which case Twilight is likely better.
If you do have several good operatives or just lots of investment into your 4*'s, then Amarna is likely the better logistics squad for Little Sunshine, and is what I'd consider her ideal endgame set, but Twilight is a great squad if you already have it and want to just keep using that.
For the Special talent, you want +8.5% Thermal Damage, to boost the Thermal damage of her Support Skill, which also boosts her own dps should you ever use her as a main dps.
For basic stats you want +10.0% ATK, as the extra Thermal damage per-shot Fritia adds is based on Fritia's ATK, not the ATK of the deployed operative.
Increasing Fritia's ATK also boosts the ATK buff granted by Strawberry Shortcake.
For the other basic stat you have three real options:
Alignment Index - Alignment Index gives the full squad more dmg dealt to Burning targets.
Given that 106 Alignment Index is only 1.06% extra damage dealt, even a maxed Alignment Index roll is not a huge percentage increase.
Skill Haste - Little Sunshine's Support Skill has a 10s duration and a 15s cooldown, so Skill Haste is useful to increase the uptime on her support skill.
With enough Skill Haste, Fritia can use her support skill every 10s, giving it 100% uptime.
With M3 Fritia can extend her support skills duration by another 10s, which should give it enough duration that Skill Haste isn't needed.
S-Energy Regen - All operatives naturally regen 1 S-Energy per second. Fritia's Support skill uses 30 S-Energy and has a 15s cooldown.
This means she uses more S-Energy than she recovers.
S-Energy Regen is thus extremely useful for longer fights, as it allows her to use her Support Skill more often.
S-Energy regen also allows her to use her Support Skill more often, increasing the uptime on her Strawberry Shortcake weapon buff.
Fritia's Support Skill has an S-Energy cost of 30, meaning Fritia can run out of S-Energy extremely quickly.
With M3 her Support Skill has a max duration of 20s (and probably closer to 13s in practice), so Fritia is using 30 S-Energy every 13-20s.
For longer fights S-Energy Regen is thus Fritia's best stat, as it allows her to use her SUpport Skill much mnore often.
For shorter fights where only 1-2 casts of her Support Skill are needed, Fritia wants Alignment Index to maximize her damage.
Overall I'd heavily recommend S-Energy Regen as Fritita's second basic stat after ATK.
If you don't have her M3 buff, then Skill Haste is a good stat too, as it allows her higher uptime on her support skill, although you may wish to have one or two S-Energy Regen mods as well to help her in longer fights too.
Skill Haste maths:
Skill Haste formula:
Skill Haste works as a CD/(1+X) modifier.
A max Skill Haste roll is 19.3.
19.3 Skill Haste = 83.8% of normal cooldown
38.6 Skill Haste = 72.15% of normal cooldown
57.9 Skill Haste = 63.33% of normal cooldown
Since Fritia has 66% uptime already (10s duration on a 15s cd), she'd need to reduce her cd by 33% in order to have 100% uptime on her buff.
Two maxed-roll Skill Haste buffs will give her support skill a cd of 10.82 seconds, which is generally all she needs in practice.
If you didn't have M3, and wanted to use Fritia for shorter fights, then 2x Skill Haste + 1x Alignment Index is her best combo.
You'll need to re-roll this when you get M3 anyway, so it's not worth re-rolling to get Skill Haste.
Again though - Since Fritia is a 4* operative, she's not worth using re-rolls on, but if you did want to, then ATK and S-Energy Regen are the two stats you try to get.
Skill Haste is a decent stat, but it's extremely niche and much worse than S-Energy Regen.