Am I being retaliated for filing for FMLA?

I recently filed for intermittent FMLA due to missing work because of severe migraines. I missed work this passed Wednesday due to this. My FMLA paperwork has not been approved yet as I have not received it yet. I also have 2 days of vacation coming up in 2 weeks. My supervisor informed me that I had enough PTO to cover my absence on Wednesday but nit enough time to take my 2 vacation days. I asked what my consequences would be if I did take them. I was then informed that she was advised by HR to give me a verbal warning due to my absences for the year. I have never been given any warnings or writes ups in the past. But now that I am questioning my PTO & right after filing for FMLA, I am given a write up. Is this considered retaliation?