Bad blood indeed.

Matty Healy’s mom, Denise Welch, isn’t over the “heartbreak” her son endured after his short-lived romance with Taylor Swift ended — that’s why she couldn’t stay quiet on “Watch What Happens Live with Andy Cohen” Thursday.

“It’s a horrible thing to have the most famous person in the world saying that your son broke her heart when it was the other way around, and then you can’t even defend yourself,” a source told Us Weekly Saturday.

They added, “She’s saying the mother-in-law stuff because that’s where Matty thought it was headed. She’s entitled to her opinion.”

An insider said Taylor Swift “broke” Matty Healy’s heart — not the other way around.Claude Yao Sahi @hijoshotit / Shutterstock

“It’s a horrible thing to have the most famous person in the world saying that your son broke her heart when it was the other way around,” the source told Us Weekly.

Reps for Welch and Healy did not immediately return Page Six’s request for comment.

When asked by Andy Cohen what she thought of Swift’s “Tortured Poet’s Department” album — purported to be about The 1957 frontman and his romance with the singer that lasted only about a month in May 2023 — Welch declared that “not being her mother-in-law is a role that I am glad that I lost.”

As the audience gasped, the “Celebrity Big Brother UK” star, 67, quickly added that she doesn’t “have anything against [Swift] at all,” and called the situation “tricky.”

The 1975 frontman and Swift dated briefly in May 2023.GC Images

Welch told Andy Cohen on Thursday’s episode of “Watch What Happens Live” that “not being her mother-in-law is a role that I am glad that I lost.”Bravo

“She — listen, you’re not allowed to say anything, and then she writes a whole album about it,” Welch said of the “Love Story” hitmaker.

Us Weekly’s insider said it’s been difficult for Welch to keep quiet when it comes to her son’s former romance.

“Any mum can imagine what it would feel like — but then you have to multiply it by a million because of how famous [Taylor] is,” they told the outlet.

“I wish I could say she’s used to it, but she’s not.”

“You have to multiply it by a million because of how famous [Taylor] is,” the insider said of the impact to Welch, seen here on “WWHL” with Cohen and “RHOC” star Shannon Beador.Bravo

The insider alleged that the split was “terrible” for Healy.GC Images

The source also said that the reality star “is still Matty’s mum at the end of the day, and it was bloody hard for her to stay quiet during the whole ordeal.”

“Now that time has gone by, she’s saying what she can because she knows that her son got hurt.”

The insider asserted that “you can’t blame a mum for standing up for her 𝘤𝘩𝘪𝘭𝘥,” and called their split “terrible” for Healy.

The “Cruel Summer” singer in now in a high-profile romance with Travis Kelce.Travis Kelce/Instagram

Healy is engaged to model Gabbriette Bechtel.TheImageDirect.com

Swift, 35, has since gone on to a widely publicized relationship with Kansas City Chiefs tight end Travis Kelce, while Healy, 36, is engaged to model and actress Gabbriette Bechtel.

On “Watch What Happens Live,” Welch insisted the family has “moved on” from the alleged drama.

“He is very happy with his amazing fiancée Gabriella, who is gorgeous,” she said.