Evicting house guest/tenant

[James Forester]

I'm in Portland OR. Around Thanksgiving, my wife's friend wanted to stay with us while she looked for her own place. It was only supposed to be a few weeks. In January, I told her she couldn't stay for free anymore. She payed $500. I told her that I'd give her an official 30 day notice on April 1st and she was to be gone may 1st. Now I find out that Portland requires 90 day notices. So, I need to get her one ASAP. Anyone know what form I should use or have any other advice?