Invited to wedding shower but haven’t talked in years

I have a friend from HS and she invited me to her wedding shower on Sunday. She invited me 1 month ago and I said I’d go. It’s super fun and all, but the only communication we have over the last 5 years is through snap. In HS she always forgot my birthday and we hung out maybe 2 times in the last 7 years. I feel a bit under the weather and super busy with work. I want to support her, but it feels weird to me to not talk to someone for so long then pretend you’re amazing friends