How do I (30F) convince my mother (66F) to go to therapy?

Before I get into this, I would like to make some things very clear.

1) My mother (66F) is not anti-therapy. She put me (30F) in therapy as a kid the first time I lost a relative, when she realized just how badly it was impacting me and that I needed help dealing with the loss (it was a grandparent who died of natural causes). She paid for my therapy all through college and still helps pay for it now when money is tight. She knows the good it does me and even nudges me gently when I’ve been too long without an appointment, which is something I have asked her to do so I don’t “fall off the wagon,” so to speak.

2) My mother’s relationships with both myself and my father/her husband (63M) are healthy, and I am an only child. My interest into getting her into therapy is for her own wellbeing.

3) I do not believe there is a danger of physical harm to herself or others, but I believe therapy would improve her self-image and quality of life.

4) Assuming that she’s telling me the truth, her reluctance to go to therapy is not an issue of pride, but due to poor experiences she’s had with therapists in the past. I don’t know details about this, and of course she’s not obligated to tell me.

With all of that established, my mother is a smart, hardworking, and caring person. However, I’ve observed a pattern that has me worried. If she does something wrong/says something incorrect, she’ll respond in a very self-depricating way. For example;

• She might use a word or phrase that has taken on a new meaning/implication in recent years that isn’t what she intends to mean. When I tell her what people my age or younger will think she means if she says that, she may say something like, “I guess I should just stop talking, then.” I know that written out this sounds like something snarky or snappish, but she says it in a sad/glum tone, like she thinks she’s stupid.
• If it’s one of those days where several things have gone wrong, when something finally goes right, rather than being relieved or happy, she’ll glumly say, “I guess I’m still good for something.”

I’m worried by this pattern of punching down at herself when she makes an honest mistake or things just aren’t working out as hoped. Myself and dad talking to her doesn’t seem to be doing any good against this. I’ve told her a few times that I think she should try going to therapy and that this pattern worries me, but she gets uncomfortable or brushes it off when I bring it up. I know nobody is happy 100% of the time, that’s not human. But she deserves to feel better about herself. Is there any way I can convince her that therapy will be good for her?

TL:DR, I’m pretty sure therapy would be good for my mother’s mental health and self-image. How do I convince her to go?