I agree with what others said, you may be admitted to UCSD, but it is definitely not a likely.
Your title mentions T15. In your post, you mention that your parents won’t pay for anything less than T15 or “well known” schools. That is a high line to draw in the sand. To me, it sounds like they want you to attend a state school.
Look at other UCs as well as SLO. Spend time working on your UC Personal Insight Questions as well as your descriptions of your 20 Activities and Awards. Don’t assume the UCs are a sure thing and leave that application until the end.