CA sales tax (eBay and parchmart)

I'm a CPA and don't know a ton on sales tax. I know the basics, but my sister's friend is doing a ton of sales on eBay and parchmart. I told her it's help her on advice.

she's making pretty good sales and she got a 1099 from eBay and parchmart for her sales and CA was notified. and they are wanting her to fill out a sales tax return.

she said eBay and Parchmart are collecting sales tax on every sale she makes. I'm assuming this is true. haven't verified. if anyone knows lmk.

if this is the case, what line on the sales tax form does she list all her sales that eBay and parchmart collected says tax on. that reduce her sales tax she owes to $0, or can she be exempt from filing.

would it be line 10 on section A that she explains that eBay and parchmart collect. Ava she doesn't owe any.

any help would d be appreciated.