How do you deal with a rude grandmother?

I started cutting when I was 14, so far I've been 6 months clean. Of course I have scars on my body, scars that I've been ashamed of and struggling with. I made lots of mistakes in my youth that I'm paying for now.
A couple months ago she pointed out my scars and asked if I was "still doing that crap"
I told her these were old scars but they just look bad because of how deep I cut.

My grandmother is never kind when she approaches the subject, never tries to make me feel better. She only makes me feel like I'm an embarrassment.

Well today she saw the same scars that she pointed out a couple months ago, and with attitude asked if I was still doing "that immature shit"
I told her these are the same ones you already pointed out. Here's how the conversation went:
Grandma: well they sure do look fresh
Me: it's because of how deep I cut
Grandma: are you even doing anything for them?
Me: Yes grandma, I put oil on them.
Grandma: Well it looks like it's not working, you should be putting ointment on them.
Me: Please, they are my scars to deal with.

Grandma: Oh? Are you proud of them?
Me: No of course not, I'm ashamed of them and you're making me feel worse. I know you think they're an eyesore and an embarrassment.

Grandma: *scoffs*
Me: I know you love me but you're overstepping boundaries.
Grandma: *yells* NO I AM NOT
Me: *walks away* bc once the yelling starts, you can't have a normal conversation with her.
She always makes me feel like shit about them and tries and to tell me what to do with them, not bc she cares but bc they are an "embarrassment"
How do you deal with a rude grandmother?
How do you deal with a rude grandmother?
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