I personally don't believe the two look alike. Sure they're both spiders so they have 8 legs and they also sport the popular black widow color palate. Overall, in both their designs, they are completely different.
Elise looks as if she is covered in pointy armor. Her limbs also look sharper, almost blade like.
Broodmother has a very rounded body. Her two front legs are the only deadly looking ones that they emphasized by making them redder than the rest.
The color palate is actually only the same when comparing the original Broodmother (in the gif) with Elise. In the comparison photo (the jpg) you can see that they changed the Brood mother from an almost solidly red body with a bit of black all over the legs to a now dark blue body with a red emphasis on the forelegs and red stripes on all the rest.
Elise's armored body causes her to really stand out compared to Broodmother causing her (in my eyes) to look much more menacing. They both have that classic red hourglass of a black widow on their backs, but you cannot really say that Elise is copying Broodmother there so much as copying the original black widow spider (same goes for the color palate choice). Elise's body proportions are also quite different than the Broodmother's, sporting a very large hindquarters, with a relatively small head. While Broodmother has a relatively uniform body shape.
Well, I've gone on enough...