I don't really see the guilt trip you mention. It's a short, informal response that offers an apology and explains Pippa's slow response (so people understand why Pippa was slow to respond if they didn't already), says that Pippa still wants to collab, and has some open-ended questions to get collab ideas flowing again and let Pippa show she's genuinely interested in the collab stream. She can tailor this message for specific conversations, it's not a boilerplate message she should just send out to everyone.
I would also suggest Pippa also talks with her manager if she's worried, they've helped her with coming up with good DM messages before.