I was playing 
and was doing my W/Q combo and the enemy 
negated everything with just one E (neither my W knocked her back nor my Q knocked her airborne). There wasn't a 
in the match, nor did she buy 
. It's like she had a spell shield for a brief duration rather than for the next ability. This was on an ARAM.
Pretty sure there is about .5 of second after spellshield deactivates where it can still block spells, that are already in progress. EG, you casted W and it was blocked, but you also hit E before your W hit, so it was also blocked. As a side note, Sivir can completely negate a ziggs ult with her shield. Was in a game a while back where a ziggs could have gotten 2-3 of my teamates in his ult, so I ran back and used E and his bomb sort of disappeared.
This is intended. Spell shields can block multiple spells at the same time if those spells land within a very small window of time. With Alistar's W/Q combo, his Q lands pretty much instantly after his W, so because they hit Sivir at almost exactly the same time, Sivir's spell shield will block both spells.
