I’m a single woman and I’ve never felt unsafe in that neighborhood. Boston in general is one of the safer cities in the US and Cambridge is one of the safer areas of Boston. You’ll need to follow basic city safety rules but shouldn’t have any issues (don’t wear both headphones, don’t pull out valuables or money on the sidewalk, don’t engage with any panhandlers, etc.).

If it’s particularly late (or you’ve been drinking) I would maybe recommend getting an Uber (likely under $20) but that’s not based on any specific risk to that neighborhood. Just a general safety tip. Also remember that the T stops running by 1am (so if you plan to stay out late make sure you budget for an Uber).