Hello leiselmum,
I don't know how old is your child (if she's a young or a little girl) but I agree, in part, with your husband.
If you need time, you need time.
But don't be too upfront or else maybe you wouldn't be able to go for another excursion later on.
... Mothers can be awful sometimes: no boudaries, no politeness at all.
Or in such a hurry because they can feel so lonely.
Some are wonderful to know but also some others are to be avoided - at least for the moment.
Until you feel strong enough to endure them, if you want to.
Tell her you need time, ask her to leave you her telephone number if she wishes to and not to call please until you do.
... Or maybe, you'll see each other at another meeting, with the others.
Let the door opened if I may say so but don't let her in until you know her better and there's no urge for it - at least, not for you, not for the moment.
(Excuse the poor english: it's not my native language.)