I am not a fan of Graf or Seles but since your clearly Seles nutter arguments are so intriguing I will answer this too as it is another funny one.
Graf's peak years were obviously 1988-1989 and 1995-1996. It is rather silly to even ask this. You are limiting Seles's peak to a 6 month period? You also conveniently start at a point directly AFTER 3 straight tournament losses to Seles, not only Wimbledon to Graf, but two others. You also imply a period Seles was winning 3 slams per year can be somehow deemed to not amongst her peak. Umm ok. Well either way I would easily take either Graf of 88-89 or 95-96 over any supposed Seles peak, even your limited version.
Graf won all 6 majors she played in 95-96, and all 8 major events counting the 2 WTA Championships. Graf won 7 of 8 majors and lost 7-5 in the finals of the other, and had something like a total 170-5 record over 2 years. I dont believe any version of Seles that ever existed was capable of that, nor did she ever manage to produce it. To win 13 of 14 majors in a given 4 yeras of peak tennis, either together or broken up like Graf's were, would probably require her winning 3 of 4 or 4 of 4 Wimbledons, the thought of alone which is hilarious. Furthmore this peak Seles you refer to lost a set to Julie Halard in her Australian Open win, and lost a match to a 36 year old Navratilova something that I cant imagine peak Graf (remember referring only to 88-89 or 95-96 Graf, not less outstanding versions of somewhat prime Graf) ever doing, especialy when she didnt lose a single match to 31 year old Navratilova in 88-89. So the answer all around is quite easy, yes still Graf no problems.
Even if you choose to protest to know like the genie years into the future you think you are that Graf wouldnt have had her 95-96 success without the Seles stabbing, that obviously in no way can apply to 88-89. Meanwhile any whining that 88-89 Graf didnt face prime Navratilova (she magically exited her prime once Graf emerged, the same way you point out Graf fans claim hers magically vanished when Seles emerged, both probably are fables from butthurt fanboys on both sides more than reality), prime Seles, is no different than one saying peak Seles played Fernandez, Sanchez, Novotna, people even you deem as weak in almost all her slam finals. That and that other than a mere 4 matches with Graf in 91-92 had easy competition as you seem to deem the Graf era players easy anyway, and so on, and basically nothing more than conjecture. It is not like you can make the argument Seles had a way deeper field to face like you could with Serena when she compiled her dominant but still less dominant than Navratilova or Graf peak stats in 2002-2003. No way was that the case back then for either Graf or Seles, and Graf produced results and stats the likes of which Seles never did, and IMO Seles would never be capable of doing.