Would you tell your friend if her boyfriend was talking trash about her behind her back?

I’m dealing with a really uncomfortable situation at work involving a friend of mine, Alex. I helped her get this job when she was struggling. She’s very shy, has low self-esteem, and lost her long-term boyfriend years ago in a tragic house fire, which she’s never fully recovered from. Yesterday was the anniversary of his death.
She’s now dating a man called Dave, who left a 14-year relationship around the same time they got together. The timeline is messy and, honestly, most of us don’t believe there wasn’t overlap. Dave is inappropriate at work — he brags about their sex life, makes crude jokes, and talks badly about Alex behind her back while acting like a “nice guy” to others.
Recently, some colleagues told me he was mocking her deceased boyfriend and saying he feels like he’s competing with a dead man. It’s clear he doesn’t respect her and seems too cowardly to end the relationship, instead trash-talking her while looking for a way out.
The problem is Alex clearly loves him, and no one knows how to tell her without completely breaking her heart.

Im not that close to Alex as i was but I feel upset on her behalf. She definitely knows something is up as she's acting out and taking it out on others including a another friend of mine and his girlfriend and it clear to see its out of jealousy by the way they treat each other vs how her boyfriend treats her
Updates
5 mo
Were all terrified to tell her but feel like cowards for not
Updates
5 mo
Atm the moment I just can't bring myself to say anything im to scared as this is also my workplace and I've heard it second hand. Im just avoiding her partner and giving him the cold shoulder
Would you tell your friend if her boyfriend was talking trash about her behind her back?
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