Kristen Stewart is ''suspicious'' of Robert Pattinson's new girlfriend.

The 'Snow White and the Huntsman' star - who previously dated the 28-year-old actor - is reportedly annoyed at FKA Twigs for ''taking advantage'' of the 'Twilight' star.

A source explained to ''Kristen was already suspicious of her motives, but when she heard that FKA was straight up talking about Rob to the press, that confirmed it.

''She knows Rob wouldn't be okay with that. It's so obvious to Kristen that this girl is just taking advantage of Rob ... She's still very protective of Rob.''

Meanwhile, FKA twigs - real name Tahliah Debrett Barnett - recently admitted that she finds it ''challenging'' being Robert's girlfriend but says it is worth it because she ''loves'' him.

Discussing her popularity with paparazzi, the 'Two Weeks' hitmaker said: ''I look uncomfortable because I am uncomfortable. But then it's like, is this person in my life worth that? And he is, without question ... In comparison to how happy I am. And how I feel with him. It's 100 percent worth it.

''That side of my life [the paparazzi] is nothing to do with me. That's, like, that is the ... side of life of the man that I love. And ... when that started happening I had to. Because that is the opposite of who I am as a person, and it was weird ... Then I had to sit back and have a conversation with myself and I had to say, 'That is something really horrible.' No, not horrible, I don't find it horrible, it's something that's very challenging.''