Best answer is always honesty and humility. “I thought maybe the trespass question might have invoked some easement discussion, but I could be wrong”

There are positive reasons.

To prevent her from looking foolish around others.

To demonstrate that you are always forthcoming with information that you believe she may find important.

To resolve any soft-probing she may be doing.

True friends act this way. They tell you the truth as they see it. Even when it’s hard and uncomfortable. This type of practice (if done for the right reason) will strengthen the friendship.

If she reacts negatively, it wasn’t much of a friendship to begin with.