The 29-year-old alpine skier and Woods have been dating since March 2013. Woods was previously married to Nordegren from 2004-2010, but their relationship came to a highly-publicized end after the golfer admitted he had been unfaithful.
An insider tells Us Weekly that Vonn and Nordegren have formed an unlikely friendship. Nordegren and Woods have two children together, and she reportedly initiated a relationship with Vonn on her children's behalf.
"After meeting her, she found she actually liked her," the source says. "You'd think it would be weird, but Elin loves Lindsey and they talk all the time. Elin likes that Lindsey is a strong woman."
The trio have even gone on vacation together, and Vonn and Nordegren occasionally took off for some one-on-one time of their own while Woods stayed in with the kids.
"Lindsey is really good for Tiger," the source continues. "She's strong, opinionated, and keeps him in line. Elin found that they are very similar and have a lot in common. They laugh and talk like they have been girlfriends forever."