I feel a little 别扭。 lekal's translation can also refer the past. It's not necessary to add 了 for past tense.Thanks for your answer, Lekal! (and for including all those options)
Because the birthday was also in the past, could I add a 了 to the first part of the sentence? （“她过生日了（所以）我给她买了张礼品卡。) or would that sound 别扭？
Adding 了 would make it more than just awkward, but make it wrong, at least to me. The particle 了 suggests the perfect tense, or more generally, a connection to the actual or historical present.她过生日【了】 (所以) 我给她买了张礼品卡。
我给她买了一张礼品卡/代金卡。 colloquialI was recently wondering how to say the following sentence in Chinese: "I bought her a gift card for her birthday."
Would this be: "我（为了？对？）她买了一张礼品代金卡。"?
That's great! Thanks for letting me know which prepositions are correct here, SuperXW! 😄我给她买了一张礼品卡/代金卡。 colloquial
我为她买了一张礼品卡/代金卡。 a little more formal than 给
我为了她买了一张礼品卡/代金卡。 unnatural, too much emotion. usually 我为了她付出了很多(made a lot of effort or sacrifice)