Yes, I think it was a very strange situation to be in. The Borden house was bad enough just living in it, with no hallways and locked doors and the strain relations were under since 1885 (when Andrew gave Abby's half-sister part of the house and the 'girls' went ballistic).
There was one item I haven't noticed anyone mentioning that was taken. That was a "red Russian" pocketbook of Abby's. Abby's watch and some kind of gold chain of hers + some various trinkets of (probably costume) jewelry were taken. But the "red Russian" pocketbook was taken at that time. How many nice things did Abby have? I imagine nothing. I think these items meant a lot to her. The watch or the chain might have been heirlooms, or hold some other sentimental value. It was very cruel, if it was Lizzie, to take these specific things.
I think Abby spoke her mind. I think she stood up to Andrew, unlike all the things we have been led to believe. I would think she threw it up (no pun intended) to Lizzie, if she knew. Maybe Andrew did not tell Abby so there would be less discord in the house.
But if Lizzie were a kleptomaniac, and I think she was one, how could Andrew stop her when he did not know how? I think the robbery was done to see if something like that could work, and as a like dress rehearsal for the murders - and to establish a precedent for someone entering and committing a crime under the same circumstances the murders would take place.
When Andrew highly suspected Lizzie of the robbery, and he questioned her again and again, maybe she broke down (especially if he was told people were turning in those horse car tickets and saying Lizzie gave them to them). But maybe she blamed her kleptomania for it, when it was an out and out theft.

"Oh, yes, yes, Father! I did the robbery! But I could not help myself! I get strange feelings, Father, that make me want to take things. I didn't mean to do it!"

(in his nightcap) "I don't know what to do with you, Lizzie. If I take you to Taunton to the hospital there, they may do all sorts of things to you there, from stories I've been told. And people would know, and they would never stop their tongues from wagging. What is this - feeling you get that you speak of?"

"It is hard to explain, Father. It is almost as if I am not myself. I am suddenly obsessed with the thought of taking something, and I cannot think of anything else until I do it. Oh, Father, forgive me!"

"If this is an illness, then I cannot tell the police anything about it. I suppose you must go on living here, so that no one knows of this. But, Lizzie. I have one question."

"Anything, Father, now that you bought -
believed what I said."

"This ring you gave me ..."

"Yes, Father. I picked it up at Gifford's. Surely you knew something was wrong. Why, I didn't even finish high school."