If another baby hit yours for no reason ?

Basically my husbands aunt has this 1 year old and everyone always talks about how she hits her baby cousins all the time and bites adults, one time we went over her house my baby was like 7 months and was holding her sophie the giraffe teether while watching tv, this lil girl comes up to her snatches it from her and throws it on the floor. Yesterday was worse, she took my babys blanket and put it over my babys head and at one point tried to choke her, when my daughters lil 7 year old uncle would tell her no and put his arm around my daughter to pull her away and protect her this lil girl hit him in the face repeatedly his mom(my mil) saw and didnt do a thing and she laughed when her son was getting hit. I took my baby to my husbands brothers room and let her watch baby videos on my phone , the lil girl comes and takes the phone from her my baby just tries to lean next to her to watch (my baby is now 11 months and wasn't hitting or anything) . I turn off the phone and put it away. At this point my baby wants to be on the floor so I put her down and the lil girl is walking my baby loves watching other children but has no one to play with so sge starts crawling following this girl, the girl has one of those brushes to paint a room and she hits my baby hard twice on the head and makes her cry at this point I'm mad and annoyed so I raise my voice a bit and tell her to not be hitting my baby she then walks away and stops picking on her for the rest of the night. I hate when I tell my husband about it all he says is "kids will be kids" um no, kids understand and they should be taught not to hit. I would understand if someone is bothering your kid and your kid hits back to defend themselves but why hit a baby for no reason ? Seriously, i don't think I'm over reacting because I know all moms are over protective and I'm sure any mom would get mad if you see your baby/kid getting picked on for no reason. My husband wants me to go over again and I will not tolerate that type of behavior. I told my SIL I didn't want my daughter around her yet she still takes her around her I hate how no one says a damn thing , I will always protect my baby and I dare that girl to do something to my baby again, I will say something !