If your advice is not successfully actionable in the short-term, it may not be considered that constructive by the recipient.
So no, do not send her that feedback.
That being said, ask the organizers of the event (or the faculty in charge) to provide transcripts of the talk in advance the next time around, especially if there is any doubt about the ability of their speakers to speak English clearly.
Do not ask for the slides. The slides are designed to be incomplete (and for good reasons). What you must ask for is the transcript. And by transcript, I do not mean that the speaker should read her own transcript while giving her presentation. Reading a script, while making it sound natural, is extremely difficult.
Ideally, the speaker's own notes (the one she has on the podium) should only of consist of a few keywords and key topics that the speaker doesn't want to forget to mention during her lecture. It should not contain full sentences, let alone paragraphs. So in that sense, the lecture shouldn't match the transcript perfectly. But even when it doesn't match the lecture perfectly, a transcript for a speaker, members of the audience do not understand, can still be very useful.
Providing a transcript in advance may not be what you're used to in your academic field, but it is possible and it's actually a pretty standard practice if someone does a presentation in front of journalists (even when the speaker is a native English speaker). For journalists, supplying a transcript in advance helps catch mistakes before they get reprinted, whether the speaker makes the mistake when speaking or whether the journalist makes the mistake when quoting the spoken words of the speaker.
From the point of view of the organizers, that will require pre-screening potential speakers, by previewing previous talks, or if that's not possible, by talking to the potential speakers directly. This is also a standard practice in some Academic circles, whether the screening process is made obvious or not.
Furthermore, as a non-native English speaker myself with a pretty strong French accent, I'm suggesting that whoever does that pre-screening is a non-native English colleague with an obvious accent himself/herself.
And instead of simply rejecting a talk because the speaker has too strong of an accent, a good pre-screener should still encourage the speaker to still speak at the event, but to supply a transcript in advance at the very least (in addition to any tentative improvement to his accent or delivery), and if that transcript is not possible by a specific deadline, to reject that talk for that event.