Of course there are other ways to interpret this. Perhaps she’s so company-starved by the corona that she’s tentatively considering tolerating your presence just to have some company - though she’s not starved enough to commit to more than a single yoga session.
That interpretation is certainly possible. Is it likely? I’ll leave it to people with social skills and friends to answer that. Personally I would suggest that you refrain from assuming that this is a sex contract or something, but then I’m single so what do I know.
Well, my point is that it’s perfectly fine to go, but while you’re at it be constantly aware that your interpretation might be totally wrong - or somewhat wrong, or slightly wrong. Having hopes is fine, having interest is fine, but having expectations is only fine so long as you’re willing to accept new data in real time.
I assume you haven’t seen each other in ten years. Her interest may be tentative because she doesn’t know how you’ve held up body-wise (I think this is supported by the yoga class invite, where she is signalling that she is taking care of herself, and you declining that particular venue might indicate that you aren’t). So I think she’s interested enough to want to see you in person, but with absolutely no commitment of any kind. That’s the way I’d take it, anyway.
So I see no harm in accepting, as long as you are very clear with yourself that it may or may not lead to actual dating, and that there is no implied promise of anything more. Or what begbert2 said immediately above. (I understood what he meant by “sex contract,” some men think that any glimmer of acceptance or interest is a guarantee that they are going to get laid.)
I don’t see the last sentence as being interpreted as anything but a sign of interest. Now, it’s a sign of interest that may be reneged upon, it might be something she just said in the moment, but it’s a sign of interest or at least that she’s not averse to the possibility.