Expensive bachelorette

Hi! I need some advice because I feel so guilty.

Im a bridesmaid in my friend’s wedding. She was in my wedding. She flew to California for the weekend for my wedding. She did not go to my shower or mini Bach (it required traveling and i literally didn’t expect her to go) but instead took me away for a night.

Her bachelorette is out out of state. They want to do 4 night, 5 days. Looking at $700/person, not including food and activities.

My husband and and I are going through expensive fertility treatments that have the potential to get more expensive. I’m closely monitored at points in my cycle which require me to be in town.

Im in graduate school, and already dropped a class because it had a requirement during her wedding week.

I did not go to her bridal shower (but paid $245 for it) because it was the day before Christmas out of state where I didn’t have family, also I had to work.

We are going to Disney the month before. It’s a fully paid trip by our family and one friend as we are dealing with the stress of infertility. We went away in December for a weekend as well, but it was paid for by credit card points.

I have massive guilt about not being able to go to her bach and don’t know how to tell her without her thinking I’m blowing her off. I care about her, really wish I could go but it’s so $$$. Also, the location of her bachelorette would delay fertility treatments 6 months because of Zika and my doctors office policy.

Ideas on how to break the news? Or am I being selfish and should go?