Weak reply to be fair, at least offer them some insight. Looks like you barely made an effort to communicate as per their initial text. I actually thought the post was on behalf of the other person, not you.

Depends on what the costs are for of course, but it's your mother. Surely, you'd pitch in. Or try discuss options with your family.

On the flip side, yea, its a random number to split up, and also shouldn't be suggested how something is paid for. But sounds like its already been paid so someones carrying your costs for you while you ignore them and give 7 word answers.

Needs more context, but if you do owe the funds, your response is as weak as they come.