Red Ginger. I'm not a big fan of her but since she is from my favorite FKG Artist, I like her anyway.

Stats:
HP: She has a lot of HP. That's a good thing. It's not like she need it a lot but it's still good due to her counter ability and absorb HP.
ATK: That's low. Too low for her. Not even 7k. It's not good even for a 5*...
DEF: Not very good too. That could be not that important if she don't have Counter.
Well. She don't shines by her stats. It's not horrible but not very good.


Skill
4.3x damage to 1 enemy and absorbs HP. That's a very nice ability, nothing else to say. It make a good combo with her good HP + Counter and with her other offensive abilities.
36% skill activation is decent too. Espacially with her skill act ability.

Abilities
+30% ATK for all.
A very nice ability, both for her and for team support.

Skill Activation Rate for party members by 1.28~1.36x based on one's own Skill Level.
THAT's a good ability. A bit rare and very usefull. It goes very well with her skill. At max skill level she is almost at 50% skillact just by herself. Add 4 x1.2 skill act girl and she just reach 100% skill act.
Add 4 x1.2 skill act girl with lvl 5 skill and 36% skill act or more and your whole team has 100% skill act.
Add Rice-Choco-fritithing Lily and you will have a slightly broken offensive team.

Increases Damage of Skills for party members by 15%.
Usually I think it's not a very good ability but with her previous skill act ability and the possible team set up... it's more usefull than ever. So, good point for her. Not her best point but still good.

100% x3.75DEF Counter + Super Counter.
I'm not sure about it. It's a good ability but she can't really use it for 2 reasons. First, her DEF stat is too bad. And as rainbow, she can't boost it with a lot of equipment (ok she can but you need dupe or dressbloom. Dupe are too rare and dressboom are reserved to better counter girls). Second, she is a hard offense girl and she will not have many allies with DEF boost in her team.
But, even in non counter team, Counter is still good to make cheap damages. On herdest bosses/maps, any kind of damage is welcome.

+150 Speed.
Sorry for speed lovers, I don't think it's good at all. It was useful in the past, where some maps needed a tight speed control or for some maps farming but this time is over. Now, this kind of speed boost is as bad as ultra low speed girls. In term of abilities, it's her darkest point. I don't have her so, I will not speak for her but speed boost is just a NO for 5* when I build a team, unless I have too many low speed girls.

Conclusion
Her stats are poorly balanced but her skill+firsts 3 abilities make her strong. Her counter is not reliable but not useless. She could be excellent but her speed boost is too negative. It force a super restrictive team building, or a 4 high speed teams set up for most missions. But, thanks to the current FKG, speed is not important on most of harest missions or challanges. You don't need it on Whaleship/Nidhogg phase 1 and there is no hard to reach pests on Aqua Shadows/Nidhogg phase 2. So, even if she can't shine on story or event missions, she is a solid 6* for the hardest FKG stuff. And that's what we want for her.


Final verdict:
Due to her speed tier, she could deserve only a poor B tier but, like I said above, thanks to speed uselessness at high level, she can be higher.
Her firsts abilities combo can make miracles with the right team and she could be both a great support or a shiny heroine, depending on the team used.
I give a a nice A Tier. She could be S Tier... if we had not some other far better girls to push her in their shadows.