What if I drop mom's supplemental insurance?

You might also contact your Area Agency on Aging to see if they have someone who can help you work through this. There is a medicare group called SHIP that you can contact for information as well.
I contacted them once for a relative and I went through the Area Agency on Aging to reach them but here is a link to their website.

https://www.shiphelp.org/

Here is another link.

https://www.medicare.gov/talk-to-someone

Since you say your mom has no money, ask about Dual Coverage with Medicare/Medicaid.

If she went to the hospital w/o supplemental Medicare coverage, she'd be responsible to pay for at least 20% of the bill up to her out of pocket deductible. Look on the back of her standard issue Medicare card to see or call the number to ask specifics.

Your moms Medicare will cover hospice 100% so she really doesn't need a supplemental plan any longer. And being under hospice care your mom should no longer have to go to the hospital. If something happens you just call hospice and they will have their nurse, PA or NP come out depending on the situation.
And at the age of 98 the odds of your mom coming off of hospice is slim to none.

Her original Medicare would still cover it, but if she's on hospice would she really go to the hospital for any reason? Wouldn't she just get ramped up palliative and hospice care?

Maybe contact her supplemental insurance provider and ask. Did you look at the premiums for 2026 which just came out for Open Enrollment? They are higher (of course) and cover less (of course) with higher deductibles (of course).