Swimming pools don't have borders, this sentence wouldn't make sense! People might understand your meaning but it would be better to say 'side'. You could also say She walked to the edge of the swimming pool and jumped in.

"Border" is correct, but is not normally used and sounds weird. "Side" is also correct and better than "border", but is still a little weird. "Edge" would be the most common, as Rachel said. Or you can say "I walked up to the swimming pool and jumped in".

Yes everyone has her own mind. It's just that some are more grammatically correct than the others.

it seems that .. She walked to the BORDER f the swimming pool and jumped in.. accordingingly ...every one has his own mind yr.. well being :))

Your feeling told you the right answer, but mine didn't. So I am trying to figure out why.