Does an admin or something want to make "first contact"?
She probably doesn't know this place or lemmy exists, and if she wants to post here, like all mastodon users, could maybe do with a pointer or two (but also a warning about following this community unless she's ok with a firehose on her feed, which she might be).
Things will be easier if and when Mastodon launches group support, I imagine. However they do it - separate timeline for groups, or actual full group support - will make groups way less spammy for Masto users.
Maybe wait until that happens to reach out. Or just warn against subscribing.
I'm on the techy side of the spectrum, and I find the mastodon-lemmy interaction a bit of a challenge. It's a multi step process with some "Where am I?!" moments sprinkled in. The process will have to be streamlined for people that don't find computers fun.
On Mastodon, groups just look like spammy users (they boost every message they're mentioned in, and any post to a Lemmy group or kbin magazine silently mentions the group), so if people are already comfortable over there, it's not that big of a deal to interact with here.