Any tips on how to get grandma to let us clean under her fingernails? (Especially important now due to COVID-19)

Ask her to soak her hands in a soapy wash, or Epsom salts to draw out dirt and debris. Tell her it will be fun and relaxing.

I have to say I so get you. 6 months it took to get my 94 year old grandmother to cut her 5+inch nails... ick. She is so old school uses the hanky after blowing her nose to drying her eyes. I finally found a happy medium. Say you want to show her something. Go to a sink or bring two bowls of hot water with soap petals and get her to play with them. As you do and make sensual noises and she will want to see for herself why you are so happy. Sounds silly but it worked. Now we have graduated to the sink and was together. It's like reverse psychology... I never thought she'd come this far. But with many tears time and hope. I can eat with her without feeling that ick. Ah. Thank the lord. Or pull the cleanliness is closest to godliness... that worked for a friend... she told her not washing properly was as bad as saying the lords name in vain... yeah. Sadly we do what we must... much love and luck to you all blessings. Jo

I agree with cwillie: "She isn't out in the community picking up the virus so cleaning her hands doesn't need to go to any extraordinary measures beyond what you would normally do. Keep her nails short..." Yup.