Overall not, some words maybe, sometimes she doesn't follow grammar rules.
I am Scottish and my first language is English, I was taught the correct grammar rules yet
many of my fellow Scots do not speak English correctly. Indeed, many English people do not speak British English
any thing like it should be spoken.
Since Maria must have learned most of her Russian language skills from her parents presumably she speaks the local dialect that would have been spoken at her home.
First of all she speaks well and her accent is almost unnoticeable and I'm pretty sure in real life she is even better but in front of the cameras when she is doing interviews she is like more nervous tries to find wright words and thinks not to make mistake/say everything grammatically correct
that's why her speak in Russian doesn't look that fluent like English , when you are listening to her you will understand that - yes she is Russian , but is not living here ... although I should repeat she speaks well
P.S. even in one Russian article yesterday they write that Mash said herself ''I have that accent and it's not necessary to calm me down''