Skill rate is very common but yeah, it's not easy to reach 100% with only 4 girls (Sigilaria already take a slot and don't have skill act without her summon). You only needs x2.7 skill act for 99.9%. It's obtainable with Apple x1.6 and 3 other x1.36 skill act.
Act again is more a problem. Kinda rare for 5 allies and it's usually low (~15-20%). There is still Regrets and kindness FM for a good 25% act again.

Another way to use her may be to treat her as a regular Debuff and just pair her with another good debuff. She still have -40% Def, -40% ATK, -50% Crit and -20% Skill rate.