Advice about legality of security cameras in shared outside apartment area to catch vandals?

A friend lives in an apartment complex and has a small shared front porch area with her immediate neighbours (both their front doors open onto the space). Recently there has been some vandalism done to her property, notably the bike she has been keeping in that space that up until then had never been a problem. She strongly suspects her immediate neighbours, who have caused problems in other ways and seem to have a weird spiteful attitude towards her. She called the police after her bike was ruined but they said without witnesses they couldn't verify it was her neighbours (and that's fair enough, there's no proof). Apparently she put the bike back a couple of times but each time there was some kind of vandalism done to it. Now it has to be stored elsewhere and is a great inconvenience to her.

I suggested a small hidden camera that only pointed on her part of the porch and her property (not pointed at anyone else's windows or property) but she is hesitant about the legality. Does anyone have any advice about this? It's really frustrating me that these people are making her life difficult for seemingly no reason other than to be spiteful/get out their dumb insecurities.