A charm, you see, is something like when a girl makes a wish to be together with the person she likes.
Literal
Charm [called-って] say [nominalizer-のは] [soft-ね], girl [subj-が] liked person [with-と] tied-together [so-that-ように] wish [obj-を] cast [or-たりする] thing [copula-だよ].
おまじない 'charm / spell / superstition' is a childish/cute word for folk magic. 願をかける 'to make a wish / cast a vow' is a set phrase from shrine/temple culture. ~ように 'so that / in order to' marks the purpose. ~たりする 'things like' gives an example rather than an exhaustive list. って言うのは is the casual definition frame 'what X means is.'