You can write it up a few ways, some will sound kind and others won’t. As with many things, the emphasis you hear and the emphasis you take away may not be the same.
“Keeps turning up when she can.”
“Not as regular as he could be.”
“Makes every effort, despite their circumstances.”
“Attended only sporadically while overwhelmed by events.”
“Exhausted but still pushing, he kept showing up when time allowed.”
“With less on their plate, they’d make a much greater contribution here.”
“He balanced as best he could and made a difference when he had opportunity to.”
Perspective matters, and is a choice.