I personally prefer Ur-ma. Ur-ma sounds like the former name of Myanmar (Burma) and I always liked saying Burma because it rolled off the tongue so well, same thing with Ur-ma. As for Eer-ma, I don't know. I feel like Eer-ma doesn't suit "Irma" and should be spelt as "Erma" but then again you wouldn't pronounce "Ermintrude" as "Eer-min-chrood", would you? You could spell Eer-ma as Earma but you wouldn't pronounce "Earnestine" as "Eer-nes-teen", would you? Plus the Ear part would cause teasing. Tl;dr: I prefer Ur-ma over Eer-ma as the pronunciation for Irma.
• https://en.wiktionary.org/wiki/Irma#Dutch (in English)
• https://nl.wiktionary.org/wiki/Irma (in Dutch)
• https://nl.forvo.com/search/Irma/nl/ (in Dutch)
• https://youtube.com/shorts/WZNLth3Z8B8 (in Dutch; the name is said at 0:01)
Converted to IPA, it should be: /'ɪr.ma:/ [noted -ed]