AIO: Money disagreement with my girlfriend over gifts for my family

Hello,
My girlfriend and I live together, and I’m the one who pays the rent every month.

Because of that, for about a year now, when she buys things for the house or other shared expenses, she usually deducts that amount from what she gives me for rent later. We’ve been doing it this way because I don’t like constantly asking her for money afterwards if I’ve already paid for everything upfront.

About a month ago, she suggested that when we visit my parents, we should bring them some gifts. We started looking together and ended up choosing a perfume for my dad, a necklace for my mom, and a backpack for my brother.

She was the one checking options, we discussed them together, agreed on them together, and she said she would order them.

Today I paid the rent, and I told her it was actually better that she had ordered the gifts instead of me, because I don’t like asking for money later, so this way she could just deduct it from the rent like we normally do with other expenses.

Then she replied: “Oh, but am I paying for the gifts too? I thought you were going to pay for all of them.”

That completely threw me off.

It was her idea to bring gifts, she looked for them, we both agreed on them, and she ordered them. Now she says that since they are my parents, paying for the gifts is my responsibility only.

From my point of view, if we both decided to bring gifts as a couple, then it makes sense that both of us contribute, especially since we already have this system where expenses are often adjusted through rent.

Am I being unreasonable for assuming she would cover at least part of it, or is it fair for her to say that gifts for my family are entirely my expense?