EXCLUSIVE: Alyssa Milano on Shannen Doherty's Cancer Battle: 'It's Heartwarming and Gut-Wrenching All at the S

The 43-year-old actress also opened up to ET about her recent 'Who's the Boss?' reunion and being 'so proud' of Danny Pintauro.

Alyssa Milano is sending lots of well wishes to Shannen Doherty.

The former Charmed co-stars have re-connected in the wake of Doherty's stunning breast cancer diagnosis, with Milano telling ET that she continues to reach out to Doherty regularly on social media. 

WATCH: Rose McGowan Writes Emotional Letter to Shannen Doherty Amid Cancer Battle: 'We Were Pitted Against Each Other' 

"I've reached out to her, yes, and I try to continue to reach out to her once a week," Milano told ET on Tuesday. "I tweeted, I [direct messaged] her and I obviously told her my concern and how everyone was on her side, and we're all supporting her, and she was very appreciative that I reached out, which was very sweet."

Though the actresses have famously had their differences since sharing the screen more than 15 years ago, Milano had nothing but kind words for Doherty.

"It's such a horrible, horrible, horrible, horrible illness, so to see anyone struggle like that in such a public way is heartwarming and gut-wrenching all at the same time," she said.

RELATED: Shannen Doherty Reveals Her Hair Is Growing Back After Chemo in Sweet Photo With Her Husband 

In a more lighthearted reunion, Milano met up with her former Who's the Boss? co-stars last week to reminisce about their time on the beloved '80s sitcom.

"We had the best time," Milano gushed.

"Tony [Danza] came in and he was like a tornado, and everyone was so excited to see him. And then he said, 'Just wait here, one second, I got to go get Lucy.' We were like, 'Lucy? Who is Lucy? Is it a new dog? Like, what is Lucy?'" she recalled. "He brought us this little ukulele that he named Lucy that apparently he taught himself how to play a couple years ago and he serenaded us for like a good 15 minutes, and it was so sweet. Judith [Light] and I, of course, we just melted."

Who's the Boss? wrapped in 1992, but Milano said that the tight-knit cast has managed to stay in touch in recent years with the help of social media.

WATCH: Alyssa Milano Talks Post-Baby Fashion, Motherhood and a Possible 'Charmed' Reunion 

"It's such a weird thing because when our show ended, nobody texted, there wasn't Facebook, there wasn't social media, so it was a lot harder to keep in touch with people," she said. "There were many lost years, but now it's so convenient to just be able to send a text and say, 'Thinking about you!' and 'Love you!' It's made it a lot easier, so we talk to each other all the time."

"Danny [Pintauro] is doing really well too," she added. "[He's] just so brave in coming out as HIV positive and all of his advocacy that he's been doing. We're all so very proud of him."

ET caught up with Milano at the Los Angeles Rams' practice facility in Thousand Oaks, California, where she also opened up about creating her highly successful NFL clothing line, Touch, and making Atkins-friendly game day snacks for the whole family. For more from the interview, tune in to Entertainment Tonight on Thursday. 

WATCH: From Gisele Bundchen to Fergie, Here Are 9 Starlets Who Love Football!